base on An opinionated framework for creating REST-like APIs in Ruby.  [](http://badge.fury.io/rb/grape) [](https://github.com/ruby-grape/grape/actions) [](https://codeclimate.com/github/ruby-grape/grape) [](https://coveralls.io/github/ruby-grape/grape?branch=master) [](https://inch-ci.org/github/ruby-grape/grape) [](https://gitter.im/ruby-grape/grape?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) ## Table of Contents - [What is Grape?](#what-is-grape) - [Stable Release](#stable-release) - [Project Resources](#project-resources) - [Grape for Enterprise](#grape-for-enterprise) - [Installation](#installation) - [Basic Usage](#basic-usage) - [Rails 7.1](#rails-71) - [Mounting](#mounting) - [All](#all) - [Rack](#rack) - [Alongside Sinatra (or other frameworks)](#alongside-sinatra-or-other-frameworks) - [Rails](#rails) - [Zeitwerk](#zeitwerk) - [Modules](#modules) - [Remounting](#remounting) - [Mount Configuration](#mount-configuration) - [Versioning](#versioning) - [Strategies](#strategies) - [Path](#path) - [Header](#header) - [Accept-Version Header](#accept-version-header) - [Param](#param) - [Describing Methods](#describing-methods) - [Configuration](#configuration) - [Parameters](#parameters) - [Params Class](#params-class) - [Declared](#declared) - [Include Parent Namespaces](#include-parent-namespaces) - [Include Missing](#include-missing) - [Evaluate Given](#evaluate-given) - [Parameter Precedence](#parameter-precedence) - [Parameter Validation and Coercion](#parameter-validation-and-coercion) - [Supported Parameter Types](#supported-parameter-types) - [Integer/Fixnum and Coercions](#integerfixnum-and-coercions) - [Custom Types and Coercions](#custom-types-and-coercions) - [Multipart File Parameters](#multipart-file-parameters) - [First-Class JSON Types](#first-class-json-types) - [Multiple Allowed Types](#multiple-allowed-types) - [Validation of Nested Parameters](#validation-of-nested-parameters) - [Dependent Parameters](#dependent-parameters) - [Group Options](#group-options) - [Renaming](#renaming) - [Built-in Validators](#built-in-validators) - [allow_blank](#allow_blank) - [values](#values) - [except_values](#except_values) - [same_as](#same_as) - [length](#length) - [regexp](#regexp) - [mutually_exclusive](#mutually_exclusive) - [exactly_one_of](#exactly_one_of) - [at_least_one_of](#at_least_one_of) - [all_or_none_of](#all_or_none_of) - [Nested mutually_exclusive, exactly_one_of, at_least_one_of, all_or_none_of](#nested-mutually_exclusive-exactly_one_of-at_least_one_of-all_or_none_of) - [Namespace Validation and Coercion](#namespace-validation-and-coercion) - [Custom Validators](#custom-validators) - [Validation Errors](#validation-errors) - [I18n](#i18n) - [Custom Validation messages](#custom-validation-messages) - [presence, allow_blank, values, regexp](#presence-allow_blank-values-regexp) - [same_as](#same_as-1) - [length](#length-1) - [all_or_none_of](#all_or_none_of-1) - [mutually_exclusive](#mutually_exclusive-1) - [exactly_one_of](#exactly_one_of-1) - [at_least_one_of](#at_least_one_of-1) - [Coerce](#coerce) - [With Lambdas](#with-lambdas) - [Pass symbols for i18n translations](#pass-symbols-for-i18n-translations) - [Overriding Attribute Names](#overriding-attribute-names) - [With Default](#with-default) - [Using dry-validation or dry-schema](#using-dry-validation-or-dry-schema) - [Headers](#headers) - [Request](#request) - [Header Case Handling](#header-case-handling) - [Response](#response) - [Routes](#routes) - [Helpers](#helpers) - [Path Helpers](#path-helpers) - [Parameter Documentation](#parameter-documentation) - [Cookies](#cookies) - [HTTP Status Code](#http-status-code) - [Redirecting](#redirecting) - [Recognizing Path](#recognizing-path) - [Allowed Methods](#allowed-methods) - [Raising Exceptions](#raising-exceptions) - [Default Error HTTP Status Code](#default-error-http-status-code) - [Handling 404](#handling-404) - [Exception Handling](#exception-handling) - [Rescuing exceptions inside namespaces](#rescuing-exceptions-inside-namespaces) - [Unrescuable Exceptions](#unrescuable-exceptions) - [Exceptions that should be rescued explicitly](#exceptions-that-should-be-rescued-explicitly) - [Logging](#logging) - [API Formats](#api-formats) - [JSONP](#jsonp) - [CORS](#cors) - [Content-type](#content-type) - [API Data Formats](#api-data-formats) - [JSON and XML Processors](#json-and-xml-processors) - [RESTful Model Representations](#restful-model-representations) - [Grape Entities](#grape-entities) - [Hypermedia and Roar](#hypermedia-and-roar) - [Rabl](#rabl) - [Active Model Serializers](#active-model-serializers) - [Sending Raw or No Data](#sending-raw-or-no-data) - [Authentication](#authentication) - [Basic Auth](#basic-auth) - [Register custom middleware for authentication](#register-custom-middleware-for-authentication) - [Describing and Inspecting an API](#describing-and-inspecting-an-api) - [Current Route and Endpoint](#current-route-and-endpoint) - [Before, After and Finally](#before-after-and-finally) - [Anchoring](#anchoring) - [Instance Variables](#instance-variables) - [Using Custom Middleware](#using-custom-middleware) - [Grape Middleware](#grape-middleware) - [Rails Middleware](#rails-middleware) - [Remote IP](#remote-ip) - [Writing Tests](#writing-tests) - [Writing Tests with Rack](#writing-tests-with-rack) - [RSpec](#rspec) - [Airborne](#airborne) - [MiniTest](#minitest) - [Writing Tests with Rails](#writing-tests-with-rails) - [RSpec](#rspec-1) - [MiniTest](#minitest-1) - [Stubbing Helpers](#stubbing-helpers) - [Reloading API Changes in Development](#reloading-api-changes-in-development) - [Reloading in Rack Applications](#reloading-in-rack-applications) - [Reloading in Rails Applications](#reloading-in-rails-applications) - [Performance Monitoring](#performance-monitoring) - [Active Support Instrumentation](#active-support-instrumentation) - [endpoint_run.grape](#endpoint_rungrape) - [endpoint_render.grape](#endpoint_rendergrape) - [endpoint_run_filters.grape](#endpoint_run_filtersgrape) - [endpoint_run_validators.grape](#endpoint_run_validatorsgrape) - [format_response.grape](#format_responsegrape) - [Monitoring Products](#monitoring-products) - [Contributing to Grape](#contributing-to-grape) - [Security](#security) - [License](#license) - [Copyright](#copyright) ## What is Grape? Grape is a REST-like API framework for Ruby. It's designed to run on Rack or complement existing web application frameworks such as Rails and Sinatra by providing a simple DSL to easily develop RESTful APIs. It has built-in support for common conventions, including multiple formats, subdomain/prefix restriction, content negotiation, versioning and much more. ## Stable Release You're reading the documentation for the next release of Grape, which should be 2.3.0. The current stable release is [2.2.0](https://github.com/ruby-grape/grape/blob/v2.2.0/README.md). ## Project Resources * [Grape Website](http://www.ruby-grape.org) * [Documentation](http://www.rubydoc.info/gems/grape) * Need help? Try [Grape Google Group](http://groups.google.com/group/ruby-grape) or [Gitter](https://gitter.im/ruby-grape/grape) * [Follow us on Twitter](https://twitter.com/grapeframework) ## Grape for Enterprise Available as part of the Tidelift Subscription. The maintainers of Grape are working with Tidelift to deliver commercial support and maintenance. Save time, reduce risk, and improve code health, while paying the maintainers of Grape. Click [here](https://tidelift.com/subscription/request-a-demo?utm_source=rubygems-grape&utm_medium=referral&utm_campaign=enterprise) for more details. ## Installation Ruby 2.7 or newer is required. Grape is available as a gem, to install it run: bundle add grape ## Basic Usage Grape APIs are Rack applications that are created by subclassing `Grape::API`. Below is a simple example showing some of the more common features of Grape in the context of recreating parts of the Twitter API. ```ruby module Twitter class API < Grape::API version 'v1', using: :header, vendor: 'twitter' format :json prefix :api helpers do def current_user @current_user ||= User.authorize!(env) end def authenticate! error!('401 Unauthorized', 401) unless current_user end end resource :statuses do desc 'Return a public timeline.' get :public_timeline do Status.limit(20) end desc 'Return a personal timeline.' get :home_timeline do authenticate! current_user.statuses.limit(20) end desc 'Return a status.' params do requires :id, type: Integer, desc: 'Status ID.' end route_param :id do get do Status.find(params[:id]) end end desc 'Create a status.' params do requires :status, type: String, desc: 'Your status.' end post do authenticate! Status.create!({ user: current_user, text: params[:status] }) end desc 'Update a status.' params do requires :id, type: String, desc: 'Status ID.' requires :status, type: String, desc: 'Your status.' end put ':id' do authenticate! current_user.statuses.find(params[:id]).update({ user: current_user, text: params[:status] }) end desc 'Delete a status.' params do requires :id, type: String, desc: 'Status ID.' end delete ':id' do authenticate! current_user.statuses.find(params[:id]).destroy end end end end ``` ## Rails 7.1 Grape's [deprecator](https://api.rubyonrails.org/v7.1.0/classes/ActiveSupport/Deprecation.html) will be added to your application's deprecators [automatically](lib/grape/railtie.rb) as `:grape`, so that your application's configuration can be applied to it. ## Mounting ### All By default Grape will compile the routes on the first route, it is possible to pre-load routes using the `compile!` method. ```ruby Twitter::API.compile! ``` This can be added to your `config.ru` (if using rackup), `application.rb` (if using rails), or any file that loads your server. ### Rack The above sample creates a Rack application that can be run from a rackup `config.ru` file with `rackup`: ```ruby run Twitter::API ``` (With pre-loading you can use) ```ruby Twitter::API.compile! run Twitter::API ``` And would respond to the following routes: GET /api/statuses/public_timeline GET /api/statuses/home_timeline GET /api/statuses/:id POST /api/statuses PUT /api/statuses/:id DELETE /api/statuses/:id Grape will also automatically respond to HEAD and OPTIONS for all GET, and just OPTIONS for all other routes. ### Alongside Sinatra (or other frameworks) If you wish to mount Grape alongside another Rack framework such as Sinatra, you can do so easily using `Rack::Cascade`: ```ruby # Example config.ru require 'sinatra' require 'grape' class API < Grape::API get :hello do { hello: 'world' } end end class Web < Sinatra::Base get '/' do 'Hello world.' end end use Rack::Session::Cookie run Rack::Cascade.new [Web, API] ``` Note that order of loading apps using `Rack::Cascade` matters. The grape application must be last if you want to raise custom 404 errors from grape (such as `error!('Not Found',404)`). If the grape application is not last and returns 404 or 405 response, [cascade utilizes that as a signal to try the next app](https://www.rubydoc.info/gems/rack/Rack/Cascade). This may lead to undesirable behavior showing the [wrong 404 page from the wrong app](https://github.com/ruby-grape/grape/issues/1515). ### Rails Place API files into `app/api`. Rails expects a subdirectory that matches the name of the Ruby module and a file name that matches the name of the class. In our example, the file name location and directory for `Twitter::API` should be `app/api/twitter/api.rb`. Modify `config/routes`: ```ruby mount Twitter::API => '/' ``` #### Zeitwerk Rails's default autoloader is `Zeitwerk`. By default, it inflects `api` as `Api` instead of `API`. To make our example work, you need to uncomment the lines at the bottom of `config/initializers/inflections.rb`, and add `API` as an acronym: ```ruby ActiveSupport::Inflector.inflections(:en) do |inflect| inflect.acronym 'API' end ``` ### Modules You can mount multiple API implementations inside another one. These don't have to be different versions, but may be components of the same API. ```ruby class Twitter::API < Grape::API mount Twitter::APIv1 mount Twitter::APIv2 end ``` You can also mount on a path, which is similar to using `prefix` inside the mounted API itself. ```ruby class Twitter::API < Grape::API mount Twitter::APIv1 => '/v1' end ``` Declarations as `before/after/rescue_from` can be placed before or after `mount`. In any case they will be inherited. ```ruby class Twitter::API < Grape::API before do header 'X-Base-Header', 'will be defined for all APIs that are mounted below' end rescue_from :all do error!({ "error" => "Internal Server Error" }, 500) end mount Twitter::Users mount Twitter::Search after do clean_cache! end rescue_from ZeroDivisionError do error!({ "error" => "Not found" }, 404) end end ``` ## Remounting You can mount the same endpoints in two different locations. ```ruby class Voting::API < Grape::API namespace 'votes' do get do # Your logic end post do # Your logic end end end class Post::API < Grape::API mount Voting::API end class Comment::API < Grape::API mount Voting::API end ``` Assuming that the post and comment endpoints are mounted in `/posts` and `/comments`, you should now be able to do `get /posts/votes`, `post /posts/votes`, `get /comments/votes` and `post /comments/votes`. ### Mount Configuration You can configure remountable endpoints to change how they behave according to where they are mounted. ```ruby class Voting::API < Grape::API namespace 'votes' do desc "Vote for your #{configuration[:votable]}" get do # Your logic end end end class Post::API < Grape::API mount Voting::API, with: { votable: 'posts' } end class Comment::API < Grape::API mount Voting::API, with: { votable: 'comments' } end ``` Note that if you're passing a hash as the first parameter to `mount`, you will need to explicitly put `()` around parameters: ```ruby # good mount({ ::Some::Api => '/some/api' }, with: { condition: true }) # bad mount ::Some::Api => '/some/api', with: { condition: true } ``` You can access `configuration` on the class (to use as dynamic attributes), inside blocks (like namespace) If you want logic happening given on an `configuration`, you can use the helper `given`. ```ruby class ConditionalEndpoint::API < Grape::API given configuration[:some_setting] do get 'mount_this_endpoint_conditionally' do configuration[:configurable_response] end end end ``` If you want a block of logic running every time an endpoint is mounted (within which you can access the `configuration` Hash) ```ruby class ConditionalEndpoint::API < Grape::API mounted do YourLogger.info "This API was mounted at: #{Time.now}" get configuration[:endpoint_name] do configuration[:configurable_response] end end end ``` More complex results can be achieved by using `mounted` as an expression within which the `configuration` is already evaluated as a Hash. ```ruby class ExpressionEndpointAPI < Grape::API get(mounted { configuration[:route_name] || 'default_name' }) do # some logic end end ``` ```ruby class BasicAPI < Grape::API desc 'Statuses index' do params: (configuration[:entity] || API::Entities::Status).documentation end params do requires :all, using: (configuration[:entity] || API::Entities::Status).documentation end get '/statuses' do statuses = Status.all type = current_user.admin? ? :full : :default present statuses, with: (configuration[:entity] || API::Entities::Status), type: type end end class V1 < Grape::API version 'v1' mount BasicAPI, with: { entity: mounted { configuration[:entity] || API::Entities::Status } } end class V2 < Grape::API version 'v2' mount BasicAPI, with: { entity: mounted { configuration[:entity] || API::Entities::V2::Status } } end ``` ## Versioning You have the option to provide various versions of your API by establishing a separate `Grape::API` class for each offered version and then integrating them into a primary `Grape::API` class. Ensure that newer versions are mounted before older ones. The default approach to versioning directs the request to the subsequent Rack middleware if a specific version is not found. ```ruby require 'v1' require 'v2' require 'v3' class App < Grape::API mount V3 mount V2 mount V1 end ``` To maintain the same endpoints from earlier API versions without rewriting them, you can indicate multiple versions within the previous API versions. ```ruby class V1 < Grape::API version 'v1', 'v2', 'v3' get '/foo' do # your code for GET /foo end get '/other' do # your code for GET /other end end class V2 < Grape::API version 'v2', 'v3' get '/var' do # your code for GET /var end end class V3 < Grape::API version 'v3' get '/foo' do # your new code for GET /foo end end ``` Using the example provided, the subsequent endpoints will be accessible across various versions: ```shell GET /v1/foo GET /v1/other GET /v2/foo # => Same behavior as v1 GET /v2/other # => Same behavior as v1 GET /v2/var # => New endpoint not available in v1 GET /v3/foo # => Different behavior to v1 and v2 GET /v3/other # => Same behavior as v1 and v2 GET /v3/var # => Same behavior as v2 ``` There are four strategies in which clients can reach your API's endpoints: `:path`, `:header`, `:accept_version_header` and `:param`. The default strategy is `:path`. ### Strategies #### Path ```ruby version 'v1', using: :path ``` Using this versioning strategy, clients should pass the desired version in the URL. curl http://localhost:9292/v1/statuses/public_timeline #### Header ```ruby version 'v1', using: :header, vendor: 'twitter' ``` Currently, Grape only supports versioned media types in the following format: ``` vnd.vendor-and-or-resource-v1234+format ``` Basically all tokens between the final `-` and the `+` will be interpreted as the version. Using this versioning strategy, clients should pass the desired version in the HTTP `Accept` head. curl -H Accept:application/vnd.twitter-v1+json http://localhost:9292/statuses/public_timeline By default, the first matching version is used when no `Accept` header is supplied. This behavior is similar to routing in Rails. To circumvent this default behavior, one could use the `:strict` option. When this option is set to `true`, a `406 Not Acceptable` error is returned when no correct `Accept` header is supplied. When an invalid `Accept` header is supplied, a `406 Not Acceptable` error is returned if the `:cascade` option is set to `false`. Otherwise a `404 Not Found` error is returned by Rack if no other route matches. Grape will evaluate the relative quality preference included in Accept headers and default to a quality of 1.0 when omitted. In the following example a Grape API that supports XML and JSON in that order will return JSON: curl -H "Accept: text/xml;q=0.8, application/json;q=0.9" localhost:1234/resource #### Accept-Version Header ```ruby version 'v1', using: :accept_version_header ``` Using this versioning strategy, clients should pass the desired version in the HTTP `Accept-Version` header. curl -H "Accept-Version:v1" http://localhost:9292/statuses/public_timeline By default, the first matching version is used when no `Accept-Version` header is supplied. This behavior is similar to routing in Rails. To circumvent this default behavior, one could use the `:strict` option. When this option is set to `true`, a `406 Not Acceptable` error is returned when no correct `Accept` header is supplied and the `:cascade` option is set to `false`. Otherwise a `404 Not Found` error is returned by Rack if no other route matches. #### Param ```ruby version 'v1', using: :param ``` Using this versioning strategy, clients should pass the desired version as a request parameter, either in the URL query string or in the request body. curl http://localhost:9292/statuses/public_timeline?apiver=v1 The default name for the query parameter is 'apiver' but can be specified using the `:parameter` option. ```ruby version 'v1', using: :param, parameter: 'v' ``` curl http://localhost:9292/statuses/public_timeline?v=v1 ## Describing Methods You can add a description to API methods and namespaces. The description would be used by [grape-swagger][grape-swagger] to generate swagger compliant documentation. Note: Description block is only for documentation and won't affects API behavior. ```ruby desc 'Returns your public timeline.' do summary 'summary' detail 'more details' params API::Entities::Status.documentation success API::Entities::Entity failure [[401, 'Unauthorized', 'Entities::Error']] default { code: 500, message: 'InvalidRequest', model: Entities::Error } named 'My named route' headers XAuthToken: { description: 'Validates your identity', required: true }, XOptionalHeader: { description: 'Not really needed', required: false } hidden false deprecated false is_array true nickname 'nickname' produces ['application/json'] consumes ['application/json'] tags ['tag1', 'tag2'] end get :public_timeline do Status.limit(20) end ``` * `detail`: A more enhanced description * `params`: Define parameters directly from an `Entity` * `success`: (former entity) The `Entity` to be used to present the success response for this route. * `failure`: (former http_codes) A definition of the used failure HTTP Codes and Entities. * `default`: The definition and `Entity` used to present the default response for this route. * `named`: A helper to give a route a name and find it with this name in the documentation Hash * `headers`: A definition of the used Headers * Other options can be found in [grape-swagger][grape-swagger] [grape-swagger]: https://github.com/ruby-grape/grape-swagger ## Configuration Use `Grape.configure` to set up global settings at load time. Currently the configurable settings are: * `param_builder`: Sets the [Parameter Builder](#parameters), defaults to `Grape::Extensions::ActiveSupport::HashWithIndifferentAccess::ParamBuilder`. To change a setting value make sure that at some point during load time the following code runs ```ruby Grape.configure do |config| config.setting = value end ``` For example, for the `param_builder`, the following code could run in an initializer: ```ruby Grape.configure do |config| config.param_builder = Grape::Extensions::Hashie::Mash::ParamBuilder end ``` You can also configure a single API: ```ruby API.configure do |config| config[key] = value end ``` This will be available inside the API with `configuration`, as if it were [mount configuration](#mount-configuration). ## Parameters Request parameters are available through the `params` hash object. This includes `GET`, `POST` and `PUT` parameters, along with any named parameters you specify in your route strings. ```ruby get :public_timeline do Status.order(params[:sort_by]) end ``` Parameters are automatically populated from the request body on `POST` and `PUT` for form input, JSON and XML content-types. The request: ``` curl -d '{"text": "140 characters"}' 'http://localhost:9292/statuses' -H Content-Type:application/json -v ``` The Grape endpoint: ```ruby post '/statuses' do Status.create!(text: params[:text]) end ``` Multipart POSTs and PUTs are supported as well. The request: ``` curl --form image_file='@image.jpg;type=image/jpg' http://localhost:9292/upload ``` The Grape endpoint: ```ruby post 'upload' do # file in params[:image_file] end ``` In the case of conflict between either of: * route string parameters * `GET`, `POST` and `PUT` parameters * the contents of the request body on `POST` and `PUT` Route string parameters will have precedence. ### Params Class By default parameters are available as `ActiveSupport::HashWithIndifferentAccess`. This can be changed to, for example, Ruby `Hash` or `Hashie::Mash` for the entire API. ```ruby class API < Grape::API include Grape::Extensions::Hashie::Mash::ParamBuilder params do optional :color, type: String end get do params.color # instead of params[:color] end ``` The class can also be overridden on individual parameter blocks using `build_with` as follows. ```ruby params do build_with Grape::Extensions::Hash::ParamBuilder optional :color, type: String end ``` Or globally with the [Configuration](#configuration) `Grape.configure.param_builder`. In the example above, `params["color"]` will return `nil` since `params` is a plain `Hash`. Available parameter builders are `Grape::Extensions::Hash::ParamBuilder`, `Grape::Extensions::ActiveSupport::HashWithIndifferentAccess::ParamBuilder` and `Grape::Extensions::Hashie::Mash::ParamBuilder`. ### Declared Grape allows you to access only the parameters that have been declared by your `params` block. It will: * Filter out the params that have been passed, but are not allowed. * Include any optional params that are declared but not passed. * Perform any parameter renaming on the resulting hash. Consider the following API endpoint: ````ruby format :json post 'users/signup' do { 'declared_params' => declared(params) } end ```` If you do not specify any parameters, `declared` will return an empty hash. **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{"user": {"first_name":"first name", "last_name": "last name"}}' ```` **Response** ````json { "declared_params": {} } ```` Once we add parameters requirements, grape will start returning only the declared parameters. ````ruby format :json params do optional :user, type: Hash do optional :first_name, type: String optional :last_name, type: String end end post 'users/signup' do { 'declared_params' => declared(params) } end ```` **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{"user": {"first_name":"first name", "last_name": "last name", "random": "never shown"}}' ```` **Response** ````json { "declared_params": { "user": { "first_name": "first name", "last_name": "last name" } } } ```` Missing params that are declared as type `Hash` or `Array` will be included. ````ruby format :json params do optional :user, type: Hash do optional :first_name, type: String optional :last_name, type: String end optional :widgets, type: Array end post 'users/signup' do { 'declared_params' => declared(params) } end ```` **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{}' ```` **Response** ````json { "declared_params": { "user": { "first_name": null, "last_name": null }, "widgets": [] } } ```` The returned hash is an `ActiveSupport::HashWithIndifferentAccess`. The `#declared` method is not available to `before` filters, as those are evaluated prior to parameter coercion. ### Include Parent Namespaces By default `declared(params)` includes parameters that were defined in all parent namespaces. If you want to return only parameters from your current namespace, you can set `include_parent_namespaces` option to `false`. ````ruby format :json namespace :parent do params do requires :parent_name, type: String end namespace ':parent_name' do params do requires :child_name, type: String end get ':child_name' do { 'without_parent_namespaces' => declared(params, include_parent_namespaces: false), 'with_parent_namespaces' => declared(params, include_parent_namespaces: true), } end end end ```` **Request** ````bash curl -X GET -H "Content-Type: application/json" localhost:9292/parent/foo/bar ```` **Response** ````json { "without_parent_namespaces": { "child_name": "bar" }, "with_parent_namespaces": { "parent_name": "foo", "child_name": "bar" }, } ```` ### Include Missing By default `declared(params)` includes parameters that have `nil` values. If you want to return only the parameters that are not `nil`, you can use the `include_missing` option. By default, `include_missing` is set to `true`. Consider the following API: ````ruby format :json params do requires :user, type: Hash do requires :first_name, type: String optional :last_name, type: String end end post 'users/signup' do { 'declared_params' => declared(params, include_missing: false) } end ```` **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{"user": {"first_name":"first name", "random": "never shown"}}' ```` **Response with include_missing:false** ````json { "declared_params": { "user": { "first_name": "first name" } } } ```` **Response with include_missing:true** ````json { "declared_params": { "user": { "first_name": "first name", "last_name": null } } } ```` It also works on nested hashes: ````ruby format :json params do requires :user, type: Hash do requires :first_name, type: String optional :last_name, type: String requires :address, type: Hash do requires :city, type: String optional :region, type: String end end end post 'users/signup' do { 'declared_params' => declared(params, include_missing: false) } end ```` **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{"user": {"first_name":"first name", "random": "never shown", "address": { "city": "SF"}}}' ```` **Response with include_missing:false** ````json { "declared_params": { "user": { "first_name": "first name", "address": { "city": "SF" } } } } ```` **Response with include_missing:true** ````json { "declared_params": { "user": { "first_name": "first name", "last_name": null, "address": { "city": "Zurich", "region": null } } } } ```` Note that an attribute with a `nil` value is not considered *missing* and will also be returned when `include_missing` is set to `false`: **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{"user": {"first_name":"first name", "last_name": null, "address": { "city": "SF"}}}' ```` **Response with include_missing:false** ````json { "declared_params": { "user": { "first_name": "first name", "last_name": null, "address": { "city": "SF"} } } } ```` ### Evaluate Given By default `declared(params)` will not evaluate `given` and return all parameters. Use `evaluate_given` to evaluate all `given` blocks and return only parameters that satisfy `given` conditions. Consider the following API: ````ruby format :json params do optional :child_id, type: Integer given :child_id do requires :father_id, type: Integer end end post 'child' do { 'declared_params' => declared(params, evaluate_given: true) } end ```` **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/child -d '{"father_id": 1}' ```` **Response with evaluate_given:false** ````json { "declared_params": { "child_id": null, "father_id": 1 } } ```` **Response with evaluate_given:true** ````json { "declared_params": { "child_id": null } } ```` It also works on nested hashes: ````ruby format :json params do requires :child, type: Hash do optional :child_id, type: Integer given :child_id do requires :father_id, type: Integer end end end post 'child' do { 'declared_params' => declared(params, evaluate_given: true) } end ```` **Request** ````bash curl -X POST -H "Content-Type: application/json" localhost:9292/child -d '{"child": {"father_id": 1}}' ```` **Response with evaluate_given:false** ````json { "declared_params": { "child": { "child_id": null, "father_id": 1 } } } ```` **Response with evaluate_given:true** ````json { "declared_params": { "child": { "child_id": null } } } ```` ### Parameter Precedence Using `route_param` takes higher precedence over a regular parameter defined with same name: ```ruby params do requires :foo, type: String end route_param :foo do get do { value: params[:foo] } end end ``` **Request** ```bash curl -X POST -H "Content-Type: application/json" localhost:9292/bar -d '{"foo": "baz"}' ``` **Response** ```json { "value": "bar" } ``` ## Parameter Validation and Coercion You can define validations and coercion options for your parameters using a `params` block. ```ruby params do requires :id, type: Integer optional :text, type: String, regexp: /\A[a-z]+\z/ group :media, type: Hash do requires :url end optional :audio, type: Hash do requires :format, type: Symbol, values: [:mp3, :wav, :aac, :ogg], default: :mp3 end mutually_exclusive :media, :audio end put ':id' do # params[:id] is an Integer end ``` When a type is specified an implicit validation is done after the coercion to ensure the output type is the one declared. Optional parameters can have a default value. ```ruby params do optional :color, type: String, default: 'blue' optional :random_number, type: Integer, default: -> { Random.rand(1..100) } optional :non_random_number, type: Integer, default: Random.rand(1..100) end ``` Default values are eagerly evaluated. Above `:non_random_number` will evaluate to the same number for each call to the endpoint of this `params` block. To have the default evaluate lazily with each request use a lambda, like `:random_number` above. Note that default values will be passed through to any validation options specified. The following example will always fail if `:color` is not explicitly provided. ```ruby params do optional :color, type: String, default: 'blue', values: ['red', 'green'] end ``` The correct implementation is to ensure the default value passes all validations. ```ruby params do optional :color, type: String, default: 'blue', values: ['blue', 'red', 'green'] end ``` You can use the value of one parameter as the default value of some other parameter. In this case, if the `primary_color` parameter is not provided, it will have the same value as the `color` one. If both of them not provided, both of them will have `blue` value. ```ruby params do optional :color, type: String, default: 'blue' optional :primary_color, type: String, default: -> (params) { params[:color] } end ``` ### Supported Parameter Types The following are all valid types, supported out of the box by Grape: * Integer * Float * BigDecimal * Numeric * Date * DateTime * Time * Boolean * String * Symbol * Rack::Multipart::UploadedFile (alias `File`) * JSON ### Integer/Fixnum and Coercions Please be aware that the behavior differs between Ruby 2.4 and earlier versions. In Ruby 2.4, values consisting of numbers are converted to Integer, but in earlier versions it will be treated as Fixnum. ```ruby params do requires :integers, type: Hash do requires :int, coerce: Integer end end get '/int' do params[:integers][:int].class end ... get '/int' integers: { int: '45' } #=> Integer in ruby 2.4 #=> Fixnum in earlier ruby versions ``` ### Custom Types and Coercions Aside from the default set of supported types listed above, any class can be used as a type as long as an explicit coercion method is supplied. If the type implements a class-level `parse` method, Grape will use it automatically. This method must take one string argument and return an instance of the correct type, or return an instance of `Grape::Types::InvalidValue` which optionally accepts a message to be returned in the response. ```ruby class Color attr_reader :value def initialize(color) @value = color end def self.parse(value) return new(value) if %w[blue red green].include?(value) Grape::Types::InvalidValue.new('Unsupported color') end end params do requires :color, type: Color, default: Color.new('blue') requires :more_colors, type: Array[Color] # Collections work optional :unique_colors, type: Set[Color] # Duplicates discarded end get '/stuff' do # params[:color] is already a Color. params[:color].value end ``` Alternatively, a custom coercion method may be supplied for any type of parameter using `coerce_with`. Any class or object may be given that implements a `parse` or `call` method, in that order of precedence. The method must accept a single string parameter, and the return value must match the given `type`. ```ruby params do requires :passwd, type: String, coerce_with: Base64.method(:decode64) requires :loud_color, type: Color, coerce_with: ->(c) { Color.parse(c.downcase) } requires :obj, type: Hash, coerce_with: JSON do requires :words, type: Array[String], coerce_with: ->(val) { val.split(/\s+/) } optional :time, type: Time, coerce_with: Chronic end end ``` Note that, a `nil` value will call the custom coercion method, while a missing parameter will not. Example of use of `coerce_with` with a lambda (a class with a `parse` method could also have been used) It will parse a string and return an Array of Integers, matching the `Array[Integer]` `type`. ```ruby params do requires :values, type: Array[Integer], coerce_with: ->(val) { val.split(/\s+/).map(&:to_i) } end ``` Grape will assert that coerced values match the given `type`, and will reject the request if they do not. To override this behaviour, custom types may implement a `parsed?` method that should accept a single argument and return `true` if the value passes type validation. ```ruby class SecureUri def self.parse(value) URI.parse value end def self.parsed?(value) value.is_a? URI::HTTPS end end params do requires :secure_uri, type: SecureUri end ``` ### Multipart File Parameters Grape makes use of `Rack::Request`'s built-in support for multipart file parameters. Such parameters can be declared with `type: File`: ```ruby params do requires :avatar, type: File end post '/' do params[:avatar][:filename] # => 'avatar.png' params[:avatar][:type] # => 'image/png' params[:avatar][:tempfile] # => #<File> end ``` ### First-Class `JSON` Types Grape supports complex parameters given as JSON-formatted strings using the special `type: JSON` declaration. JSON objects and arrays of objects are accepted equally, with nested validation rules applied to all objects in either case: ```ruby params do requires :json, type: JSON do requires :int, type: Integer, values: [1, 2, 3] end end get '/' do params[:json].inspect end client.get('/', json: '{"int":1}') # => "{:int=>1}" client.get('/', json: '[{"int":"1"}]') # => "[{:int=>1}]" client.get('/', json: '{"int":4}') # => HTTP 400 client.get('/', json: '[{"int":4}]') # => HTTP 400 ``` Additionally `type: Array[JSON]` may be used, which explicitly marks the parameter as an array of objects. If a single object is supplied it will be wrapped. ```ruby params do requires :json, type: Array[JSON] do requires :int, type: Integer end end get '/' do params[:json].each { |obj| ... } # always works end ``` For stricter control over the type of JSON structure which may be supplied, use `type: Array, coerce_with: JSON` or `type: Hash, coerce_with: JSON`. ### Multiple Allowed Types Variant-type parameters can be declared using the `types` option rather than `type`: ```ruby params do requires :status_code, types: [Integer, String, Array[Integer, String]] end get '/' do params[:status_code].inspect end client.get('/', status_code: 'OK_GOOD') # => "OK_GOOD" client.get('/', status_code: 300) # => 300 client.get('/', status_code: %w(404 NOT FOUND)) # => [404, "NOT", "FOUND"] ``` As a special case, variant-member-type collections may also be declared, by passing a `Set` or `Array` with more than one member to `type`: ```ruby params do requires :status_codes, type: Array[Integer,String] end get '/' do params[:status_codes].inspect end client.get('/', status_codes: %w(1 two)) # => [1, "two"] ``` ### Validation of Nested Parameters Parameters can be nested using `group` or by calling `requires` or `optional` with a block. In the [above example](#parameter-validation-and-coercion), this means `params[:media][:url]` is required along with `params[:id]`, and `params[:audio][:format]` is required only if `params[:audio]` is present. With a block, `group`, `requires` and `optional` accept an additional option `type` which can be either `Array` or `Hash`, and defaults to `Array`. Depending on the value, the nested parameters will be treated either as values of a hash or as values of hashes in an array. ```ruby params do optional :preferences, type: Array do requires :key requires :value end requires :name, type: Hash do requires :first_name requires :last_name end end ``` ### Dependent Parameters Suppose some of your parameters are only relevant if another parameter is given; Grape allows you to express this relationship through the `given` method in your parameters block, like so: ```ruby params do optional :shelf_id, type: Integer given :shelf_id do requires :bin_id, type: Integer end end ``` In the example above Grape will use `blank?` to check whether the `shelf_id` param is present. `given` also takes a `Proc` with custom code. Below, the param `description` is required only if the value of `category` is equal `foo`: ```ruby params do optional :category given category: ->(val) { val == 'foo' } do requires :description end end ``` You can rename parameters: ```ruby params do optional :category, as: :type given type: ->(val) { val == 'foo' } do requires :description end end ``` Note: param in `given` should be the renamed one. In the example, it should be `type`, not `category`. ### Group Options Parameters options can be grouped. It can be useful if you want to extract common validation or types for several parameters. Within these groups, individual parameters can extend or selectively override the common settings, allowing you to maintain the defaults at the group level while still applying parameter-specific rules where necessary. The example below presents a typical case when parameters share common options. ```ruby params do requires :first_name, type: String, regexp: /w+/, desc: 'First name', documentation: { in: 'body' } optional :middle_name, type: String, regexp: /w+/, desc: 'Middle name', documentation: { in: 'body', x: { nullable: true } } requires :last_name, type: String, regexp: /w+/, desc: 'Last name', documentation: { in: 'body' } end ``` Grape allows you to present the same logic through the `with` method in your parameters block, like so: ```ruby params do with(type: String, regexp: /w+/, documentation: { in: 'body' }) do requires :first_name, desc: 'First name' optional :middle_name, desc: 'Middle name', documentation: { x: { nullable: true } } requires :last_name, desc: 'Last name' end end ``` You can organize settings into layers using nested `with' blocks. Each layer can use, add to, or change the settings of the layer above it. This helps to keep complex parameters organized and consistent, while still allowing for specific customizations to be made. ```ruby params do with(documentation: { in: 'body' }) do # Applies documentation to all nested parameters with(type: String, regexp: /\w+/) do # Applies type and validation to names requires :first_name, desc: 'First name' requires :last_name, desc: 'Last name' end optional :age, type: Integer, desc: 'Age', documentation: { x: { nullable: true } } # Specific settings for 'age' end end ``` ### Renaming You can rename parameters using `as`, which can be useful when refactoring existing APIs: ```ruby resource :users do params do requires :email_address, as: :email requires :password end post do User.create!(declared(params)) # User takes email and password end end ``` The value passed to `as` will be the key when calling `declared(params)`. ### Built-in Validators #### `allow_blank` Parameters can be defined as `allow_blank`, ensuring that they contain a value. By default, `requires` only validates that a parameter was sent in the request, regardless its value. With `allow_blank: false`, empty values or whitespace only values are invalid. `allow_blank` can be combined with both `requires` and `optional`. If the parameter is required, it has to contain a value. If it's optional, it's possible to not send it in the request, but if it's being sent, it has to have some value, and not an empty string/only whitespaces. ```ruby params do requires :username, allow_blank: false optional :first_name, allow_blank: false end ``` #### `values` Parameters can be restricted to a specific set of values with the `:values` option. ```ruby params do requires :status, type: Symbol, values: [:not_started, :processing, :done] optional :numbers, type: Array[Integer], default: 1, values: [1, 2, 3, 5, 8] end ``` Supplying a range to the `:values` option ensures that the parameter is (or parameters are) included in that range (using `Range#include?`). ```ruby params do requires :latitude, type: Float, values: -90.0..+90.0 requires :longitude, type: Float, values: -180.0..+180.0 optional :letters, type: Array[String], values: 'a'..'z' end ``` Note endless ranges are also supported with ActiveSupport >= 6.0, but they require that the type be provided. ```ruby params do requires :minimum, type: Integer, values: 10.. optional :maximum, type: Integer, values: ..10 end ``` Note that *both* range endpoints have to be a `#kind_of?` your `:type` option (if you don't supply the `:type` option, it will be guessed to be equal to the class of the range's first endpoint). So the following is invalid: ```ruby params do requires :invalid1, type: Float, values: 0..10 # 0.kind_of?(Float) => false optional :invalid2, values: 0..10.0 # 10.0.kind_of?(0.class) => false end ``` The `:values` option can also be supplied with a `Proc`, evaluated lazily with each request. If the Proc has arity zero (i.e. it takes no arguments) it is expected to return either a list or a range which will then be used to validate the parameter. For example, given a status model you may want to restrict by hashtags that you have previously defined in the `HashTag` model. ```ruby params do requires :hashtag, type: String, values: -> { Hashtag.all.map(&:tag) } end ``` Alternatively, a Proc with arity one (i.e. taking one argument) can be used to explicitly validate each parameter value. In that case, the Proc is expected to return a truthy value if the parameter value is valid. The parameter will be considered invalid if the Proc returns a falsy value or if it raises a StandardError. ```ruby params do requires :number, type: Integer, values: ->(v) { v.even? && v < 25 } end ``` While Procs are convenient for single cases, consider using [Custom Validators](#custom-validators) in cases where a validation is used more than once. Note that [allow_blank](#allow_blank) validator applies while using `:values`. In the following example the absence of `:allow_blank` does not prevent `:state` from receiving blank values because `:allow_blank` defaults to `true`. ```ruby params do requires :state, type: Symbol, values: [:active, :inactive] end ``` #### `except_values` Parameters can be restricted from having a specific set of values with the `:except_values` option. The `except_values` validator behaves similarly to the `values` validator in that it accepts either an Array, a Range, or a Proc. Unlike the `values` validator, however, `except_values` only accepts Procs with arity zero. ```ruby params do requires :browser, except_values: [ 'ie6', 'ie7', 'ie8' ] requires :port, except_values: { value: 0..1024, message: 'is not allowed' } requires :hashtag, except_values: -> { Hashtag.FORBIDDEN_LIST } end ``` #### `same_as` A `same_as` option can be given to ensure that values of parameters match. ```ruby params do requires :password requires :password_confirmation, same_as: :password end ``` #### `length` Parameters with types that support `#length` method can be restricted to have a specific length with the `:length` option. The validator accepts `:min` or `:max` or both options or only `:is` to validate that the value of the parameter is within the given limits. ```ruby params do requires :code, type: String, length: { is: 2 } requires :str, type: String, length: { min: 3 } requires :list, type: [Integer], length: { min: 3, max: 5 } requires :hash, type: Hash, length: { max: 5 } end ``` #### `regexp` Parameters can be restricted to match a specific regular expression with the `:regexp` option. If the value does not match the regular expression an error will be returned. Note that this is true for both `requires` and `optional` parameters. ```ruby params do requires :email, regexp: /.+@.+/ end ``` The validator will pass if the parameter was sent without value. To ensure that the parameter contains a value, use `allow_blank: false`. ```ruby params do requires :email, allow_blank: false, regexp: /.+@.+/ end ``` #### `mutually_exclusive` Parameters can be defined as `mutually_exclusive`, ensuring that they aren't present at the same time in a request. ```ruby params do optional :beer optional :wine mutually_exclusive :beer, :wine end ``` Multiple sets can be defined: ```ruby params do optional :beer optional :wine mutually_exclusive :beer, :wine optional :scotch optional :aquavit mutually_exclusive :scotch, :aquavit end ``` **Warning**: Never define mutually exclusive sets with any required params. Two mutually exclusive required params will mean params are never valid, thus making the endpoint useless. One required param mutually exclusive with an optional param will mean the latter is never valid. #### `exactly_one_of` Parameters can be defined as 'exactly_one_of', ensuring that exactly one parameter gets selected. ```ruby params do optional :beer optional :wine exactly_one_of :beer, :wine end ``` Note that using `:default` with `mutually_exclusive` will cause multiple parameters to always have a default value and raise a `Grape::Exceptions::Validation` mutually exclusive exception. #### `at_least_one_of` Parameters can be defined as 'at_least_one_of', ensuring that at least one parameter gets selected. ```ruby params do optional :beer optional :wine optional :juice at_least_one_of :beer, :wine, :juice end ``` #### `all_or_none_of` Parameters can be defined as 'all_or_none_of', ensuring that all or none of parameters gets selected. ```ruby params do optional :beer optional :wine optional :juice all_or_none_of :beer, :wine, :juice end ``` #### Nested `mutually_exclusive`, `exactly_one_of`, `at_least_one_of`, `all_or_none_of` All of these methods can be used at any nested level. ```ruby params do requires :food, type: Hash do optional :meat optional :fish optional :rice at_least_one_of :meat, :fish, :rice end group :drink, type: Hash do optional :beer optional :wine optional :juice exactly_one_of :beer, :wine, :juice end optional :dessert, type: Hash do optional :cake optional :icecream mutually_exclusive :cake, :icecream end optional :recipe, type: Hash do optional :oil optional :meat all_or_none_of :oil, :meat end end ``` ### Namespace Validation and Coercion Namespaces allow parameter definitions and apply to every method within the namespace. ```ruby namespace :statuses do params do requires :user_id, type: Integer, desc: 'A user ID.' end namespace ':user_id' do desc "Retrieve a user's status." params do requires :status_id, type: Integer, desc: 'A status ID.' end get ':status_id' do User.find(params[:user_id]).statuses.find(params[:status_id]) end end end ``` The `namespace` method has a number of aliases, including: `group`, `resource`, `resources`, and `segment`. Use whichever reads the best for your API. You can conveniently define a route parameter as a namespace using `route_param`. ```ruby namespace :statuses do route_param :id do desc 'Returns all replies for a status.' get 'replies' do Status.find(params[:id]).replies end desc 'Returns a status.' get do Status.find(params[:id]) end end end ``` You can also define a route parameter type by passing to `route_param`'s options. ```ruby namespace :arithmetic do route_param :n, type: Integer do desc 'Returns in power' get 'power' do params[:n] ** params[:n] end end end ``` ### Custom Validators ```ruby class AlphaNumeric < Grape::Validations::Validators::Base def validate_param!(attr_name, params) unless params[attr_name] =~ /\A[[:alnum:]]+\z/ raise Grape::Exceptions::Validation.new params: [@scope.full_name(attr_name)], message: 'must consist of alpha-numeric characters' end end end ``` ```ruby params do requires :text, alpha_numeric: true end ``` You can also create custom classes that take parameters. ```ruby class Length < Grape::Validations::Validators::Base def validate_param!(attr_name, params) unless params[attr_name].length <= @option raise Grape::Exceptions::Validation.new params: [@scope.full_name(attr_name)], message: "must be at the most #{@option} characters long" end end end ``` ```ruby params do requires :text, length: 140 end ``` You can also create custom validation that use request to validate the attribute. For example if you want to have parameters that are available to only admins, you can do the following. ```ruby class Admin < Grape::Validations::Validators::Base def validate(request) # return if the param we are checking was not in request # @attrs is a list containing the attribute we are currently validating # in our sample case this method once will get called with # @attrs being [:admin_field] and once with @attrs being [:admin_false_field] return unless request.params.key?(@attrs.first) # check if admin flag is set to true return unless @option # check if user is admin or not # as an example get a token from request and check if it's admin or not raise Grape::Exceptions::Validation.new params: @attrs, message: 'Can not set admin-only field.' unless request.headers['X-Access-Token'] == 'admin' end end ``` And use it in your endpoint definition as: ```ruby params do optional :admin_field, type: String, admin: true optional :non_admin_field, type: String optional :admin_false_field, type: String, admin: false end ``` Every validation will have its own instance of the validator, which means that the validator can have a state. ### Validation Errors Validation and coercion errors are collected and an exception of type `Grape::Exceptions::ValidationErrors` is raised. If the exception goes uncaught it will respond with a status of 400 and an error message. The validation errors are grouped by parameter name and can be accessed via `Grape::Exceptions::ValidationErrors#errors`. The default response from a `Grape::Exceptions::ValidationErrors` is a humanly readable string, such as "beer, wine are mutually exclusive", in the following example. ```ruby params do optional :beer optional :wine optional :juice exactly_one_of :beer, :wine, :juice end ``` You can rescue a `Grape::Exceptions::ValidationErrors` and respond with a custom response or turn the response into well-formatted JSON for a JSON API that separates individual parameters and the corresponding error messages. The following `rescue_from` example produces `[{"params":["beer","wine"],"messages":["are mutually exclusive"]}]`. ```ruby format :json subject.rescue_from Grape::Exceptions::ValidationErrors do |e| error! e, 400 end ``` `Grape::Exceptions::ValidationErrors#full_messages` returns the validation messages as an array. `Grape::Exceptions::ValidationErrors#message` joins the messages to one string. For responding with an array of validation messages, you can use `Grape::Exceptions::ValidationErrors#full_messages`. ```ruby format :json subject.rescue_from Grape::Exceptions::ValidationErrors do |e| error!({ messages: e.full_messages }, 400) end ``` Grape returns all validation and coercion errors found by default. To skip all subsequent validation checks when a specific param is found invalid, use `fail_fast: true`. The following example will not check if `:wine` is present unless it finds `:beer`. ```ruby params do required :beer, fail_fast: true required :wine end ``` The result of empty params would be a single `Grape::Exceptions::ValidationErrors` error. Similarly, no regular expression test will be performed if `:blah` is blank in the following example. ```ruby params do required :blah, allow_blank: false, regexp: /blah/, fail_fast: true end ``` ### I18n Grape supports I18n for parameter-related error messages, but will fallback to English if translations for the default locale have not been provided. See [en.yml](lib/grape/locale/en.yml) for message keys. In case your app enforces available locales only and :en is not included in your available locales, Grape cannot fall back to English and will return the translation key for the error message. To avoid this behaviour, either provide a translation for your default locale or add :en to your available locales. ### Custom Validation messages Grape supports custom validation messages for parameter-related and coerce-related error messages. #### `presence`, `allow_blank`, `values`, `regexp` ```ruby params do requires :name, values: { value: 1..10, message: 'not in range from 1 to 10' }, allow_blank: { value: false, message: 'cannot be blank' }, regexp: { value: /^[a-z]+$/, message: 'format is invalid' }, message: 'is required' end ``` #### `same_as` ```ruby params do requires :password requires :password_confirmation, same_as: { value: :password, message: 'not match' } end ``` #### `length` ```ruby params do requires :code, type: String, length: { is: 2, message: 'code is expected to be exactly 2 characters long' } requires :str, type: String, length: { min: 5, message: 'str is expected to be atleast 5 characters long' } requires :list, type: [Integer], length: { min: 2, max: 3, message: 'list is expected to have between 2 and 3 elements' } end ``` #### `all_or_none_of` ```ruby params do optional :beer optional :wine optional :juice all_or_none_of :beer, :wine, :juice, message: "all params are required or none is required" end ``` #### `mutually_exclusive` ```ruby params do optional :beer optional :wine optional :juice mutually_exclusive :beer, :wine, :juice, message: "are mutually exclusive cannot pass both params" end ``` #### `exactly_one_of` ```ruby params do optional :beer optional :wine optional :juice exactly_one_of :beer, :wine, :juice, message: { exactly_one: "are missing, exactly one parameter is required", mutual_exclusion: "are mutually exclusive, exactly one parameter is required" } end ``` #### `at_least_one_of` ```ruby params do optional :beer optional :wine optional :juice at_least_one_of :beer, :wine, :juice, message: "are missing, please specify at least one param" end ``` #### `Coerce` ```ruby params do requires :int, type: { value: Integer, message: "type cast is invalid" } end ``` #### `With Lambdas` ```ruby params do requires :name, values: { value: -> { (1..10).to_a }, message: 'not in range from 1 to 10' } end ``` #### `Pass symbols for i18n translations` You can pass a symbol if you want i18n translations for your custom validation messages. ```ruby params do requires :name, message: :name_required end ``` ```ruby # en.yml en: grape: errors: format: ! '%{attributes} %{message}' messages: name_required: 'must be present' ``` #### Overriding Attribute Names You can also override attribute names. ```ruby # en.yml en: grape: errors: format: ! '%{attributes} %{message}' messages: name_required: 'must be present' attributes: name: 'Oops! Name' ``` Will produce 'Oops! Name must be present' #### With Default You cannot set a custom message option for Default as it requires interpolation `%{option1}: %{value1} is incompatible with %{option2}: %{value2}`. You can change the default error message for Default by changing the `incompatible_option_values` message key inside [en.yml](lib/grape/locale/en.yml) ```ruby params do requires :name, values: { value: -> { (1..10).to_a }, message: 'not in range from 1 to 10' }, default: 5 end ``` ### Using `dry-validation` or `dry-schema` As an alternative to the `params` DSL described above, you can use a schema or `dry-validation` contract to describe an endpoint's parameters. This can be especially useful if you use the above already in some other parts of your application. If not, you'll need to add `dry-validation` or `dry-schema` to your `Gemfile`. Then call `contract` with a contract or schema defined previously: ```rb CreateOrdersSchema = Dry::Schema.Params do required(:orders).array(:hash) do required(:name).filled(:string) optional(:volume).maybe(:integer, lt?: 9) end end # ... contract CreateOrdersSchema ``` or with a block, using the [schema definition syntax](https://dry-rb.org/gems/dry-schema/1.13/#quick-start): ```rb contract do required(:orders).array(:hash) do required(:name).filled(:string) optional(:volume).maybe(:integer, lt?: 9) end end ``` The latter will define a coercing schema (`Dry::Schema.Params`). When using the former approach, it's up to you to decide whether the input will need coercing. The `params` and `contract` declarations can also be used together in the same API, e.g. to describe different parts of a nested namespace for an endpoint. ## Headers ### Request Request headers are available through the `headers` helper or from `env` in their original form. ```ruby get do error!('Unauthorized', 401) unless headers['Secret-Password'] == 'swordfish' end ``` ```ruby get do error!('Unauthorized', 401) unless env['HTTP_SECRET_PASSWORD'] == 'swordfish' end ``` #### Header Case Handling The above example may have been requested as follows: ``` shell curl -H "secret_PassWord: swordfish" ... ``` The header name will have been normalized for you. - In the `header` helper names will be coerced into a downcased kebab case as `secret-password` if using Rack 3. - In the `header` helper names will be coerced into a capitalized kebab case as `Secret-PassWord` if using Rack < 3. - In the `env` collection they appear in all uppercase, in snake case, and prefixed with 'HTTP_' as `HTTP_SECRET_PASSWORD` The header name will have been normalized per HTTP standards defined in [RFC2616 Section 4.2](https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2) regardless of what is being sent by a client. ### Response You can set a response header with `header` inside an API. ```ruby header 'X-Robots-Tag', 'noindex' ``` When raising `error!`, pass additional headers as arguments. Additional headers will be merged with headers set before `error!` call. ```ruby error! 'Unauthorized', 401, 'X-Error-Detail' => 'Invalid token.' ``` ## Routes To define routes you can use the `route` method or the shorthands for the HTTP verbs. To define a route that accepts any route set to `:any`. Parts of the path that are denoted with a colon will be interpreted as route parameters. ```ruby route :get, 'status' do end # is the same as get 'status' do end # is the same as get :status do end # is NOT the same as get ':status' do # this makes params[:status] available end # This will make both params[:status_id] and params[:id] available get 'statuses/:status_id/reviews/:id' do end ``` To declare a namespace that prefixes all routes within, use the `namespace` method. `group`, `resource`, `resources` and `segment` are aliases to this method. Any endpoints within will share their parent context as well as any configuration done in the namespace context. The `route_param` method is a convenient method for defining a parameter route segment. If you define a type, it will add a validation for this parameter. ```ruby route_param :id, type: Integer do get 'status' do end end # is the same as namespace ':id' do params do requires :id, type: Integer end get 'status' do end end ``` Optionally, you can define requirements for your named route parameters using regular expressions on namespace or endpoint. The route will match only if all requirements are met. ```ruby get ':id', requirements: { id: /[0-9]*/ } do Status.find(params[:id]) end namespace :outer, requirements: { id: /[0-9]*/ } do get :id do end get ':id/edit' do end end ``` ## Helpers You can define helper methods that your endpoints can use with the `helpers` macro by either giving a block or an array of modules. ```ruby module StatusHelpers def user_info(user) "#{user} has statused #{user.statuses} status(s)" end end module HttpCodesHelpers def unauthorized 401 end end class API < Grape::API # define helpers with a block helpers do def current_user User.find(params[:user_id]) end end # or mix in an array of modules helpers StatusHelpers, HttpCodesHelpers before do error!('Access Denied', unauthorized) unless current_user end get 'info' do # helpers available in your endpoint and filters user_info(current_user) end end ``` You can define reusable `params` using `helpers`. ```ruby class API < Grape::API helpers do params :pagination do optional :page, type: Integer optional :per_page, type: Integer end end desc 'Get collection' params do use :pagination # aliases: includes, use_scope end get do Collection.page(params[:page]).per(params[:per_page]) end end ``` You can also define reusable `params` using shared helpers. ```ruby module SharedParams extend Grape::API::Helpers params :period do optional :start_date optional :end_date end params :pagination do optional :page, type: Integer optional :per_page, type: Integer end end class API < Grape::API helpers SharedParams desc 'Get collection.' params do use :period, :pagination end get do Collection .from(params[:start_date]) .to(params[:end_date]) .page(params[:page]) .per(params[:per_page]) end end ``` Helpers support blocks that can help set default values. The following API can return a collection sorted by `id` or `created_at` in `asc` or `desc` order. ```ruby module SharedParams extend Grape::API::Helpers params :order do |options| optional :order_by, type: Symbol, values: options[:order_by], default: options[:default_order_by] optional :order, type: Symbol, values: %i(asc desc), default: options[:default_order] end end class API < Grape::API helpers SharedParams desc 'Get a sorted collection.' params do use :order, order_by: %i(id created_at), default_order_by: :created_at, default_order: :asc end get do Collection.send(params[:order], params[:order_by]) end end ``` ## Path Helpers If you need methods for generating paths inside your endpoints, please see the [grape-route-helpers](https://github.com/reprah/grape-route-helpers) gem. ## Parameter Documentation You can attach additional documentation to `params` using a `documentation` hash. ```ruby params do optional :first_name, type: String, documentation: { example: 'Jim' } requires :last_name, type: String, documentation: { example: 'Smith' } end ``` If documentation isn't needed (for instance, it is an internal API), documentation can be disabled. ```ruby class API < Grape::API do_not_document! # endpoints... end ``` In this case, Grape won't create objects related to documentation which are retained in RAM forever. ## Cookies You can set, get and delete your cookies very simply using `cookies` method. ```ruby class API < Grape::API get 'status_count' do cookies[:status_count] ||= 0 cookies[:status_count] += 1 { status_count: cookies[:status_count] } end delete 'status_count' do { status_count: cookies.delete(:status_count) } end end ``` Use a hash-based syntax to set more than one value. ```ruby cookies[:status_count] = { value: 0, expires: Time.tomorrow, domain: '.twitter.com', path: '/' } cookies[:status_count][:value] +=1 ``` Delete a cookie with `delete`. ```ruby cookies.delete :status_count ``` Specify an optional path. ```ruby cookies.delete :status_count, path: '/' ``` ## HTTP Status Code By default Grape returns a 201 for `POST`-Requests, 204 for `DELETE`-Requests that don't return any content, and 200 status code for all other Requests. You can use `status` to query and set the actual HTTP Status Code ```ruby post do status 202 if status == 200 # do some thing end end ``` You can also use one of status codes symbols that are provided by [Rack utils](http://www.rubydoc.info/github/rack/rack/Rack/Utils#HTTP_STATUS_CODES-constant) ```ruby post do status :no_content end ``` ## Redirecting You can redirect to a new url temporarily (302) or permanently (301). ```ruby redirect '/statuses' ``` ```ruby redirect '/statuses', permanent: true ``` ## Recognizing Path You can recognize the endpoint matched with given path. This API returns an instance of `Grape::Endpoint`. ```ruby class API < Grape::API get '/statuses' do end end API.recognize_path '/statuses' ``` Since version `2.1.0`, the `recognize_path` method takes into account the parameters type to determine which endpoint should match with given path. ```ruby class Books < Grape::API resource :books do route_param :id, type: Integer do # GET /books/:id get do #... end end resource :share do # POST /books/share post do # .... end end end end API.recognize_path '/books/1' # => /books/:id API.recognize_path '/books/share' # => /books/share API.recognize_path '/books/other' # => nil ``` ## Allowed Methods When you add a `GET` route for a resource, a route for the `HEAD` method will also be added automatically. You can disable this behavior with `do_not_route_head!`. ``` ruby class API < Grape::API do_not_route_head! get '/example' do # only responds to GET end end ``` When you add a route for a resource, a route for the `OPTIONS` method will also be added. The response to an OPTIONS request will include an "Allow" header listing the supported methods. If the resource has `before` and `after` callbacks they will be executed, but no other callbacks will run. ```ruby class API < Grape::API get '/rt_count' do { rt_count: current_user.rt_count } end params do requires :value, type: Integer, desc: 'Value to add to the rt count.' end put '/rt_count' do current_user.rt_count += params[:value].to_i { rt_count: current_user.rt_count } end end ``` ``` shell curl -v -X OPTIONS http://localhost:3000/rt_count > OPTIONS /rt_count HTTP/1.1 > < HTTP/1.1 204 No Content < Allow: OPTIONS, GET, PUT ``` You can disable this behavior with `do_not_route_options!`. If a request for a resource is made with an unsupported HTTP method, an HTTP 405 (Method Not Allowed) response will be returned. If the resource has `before` callbacks they will be executed, but no other callbacks will run. ``` shell curl -X DELETE -v http://localhost:3000/rt_count/ > DELETE /rt_count/ HTTP/1.1 > Host: localhost:3000 > < HTTP/1.1 405 Method Not Allowed < Allow: OPTIONS, GET, PUT ``` ## Raising Exceptions You can abort the execution of an API method by raising errors with `error!`. ```ruby error! 'Access Denied', 401 ``` Anything that responds to `#to_s` can be given as a first argument to `error!`. ```ruby error! :not_found, 404 ``` You can also return JSON formatted objects by raising error! and passing a hash instead of a message. ```ruby error!({ error: 'unexpected error', detail: 'missing widget' }, 500) ``` You can set additional headers for the response. They will be merged with headers set before `error!` call. ```ruby error!('Something went wrong', 500, 'X-Error-Detail' => 'Invalid token.') ``` You can present documented errors with a Grape entity using the the [grape-entity](https://github.com/ruby-grape/grape-entity) gem. ```ruby module API class Error < Grape::Entity expose :code expose :message end end ``` The following example specifies the entity to use in the `http_codes` definition. ```ruby desc 'My Route' do failure [[408, 'Unauthorized', API::Error]] end error!({ message: 'Unauthorized' }, 408) ``` The following example specifies the presented entity explicitly in the error message. ```ruby desc 'My Route' do failure [[408, 'Unauthorized']] end error!({ message: 'Unauthorized', with: API::Error }, 408) ``` ### Default Error HTTP Status Code By default Grape returns a 500 status code from `error!`. You can change this with `default_error_status`. ``` ruby class API < Grape::API default_error_status 400 get '/example' do error! 'This should have http status code 400' end end ``` ### Handling 404 For Grape to handle all the 404s for your API, it can be useful to use a catch-all. In its simplest form, it can be like: ```ruby route :any, '*path' do error! # or something else end ``` It is very crucial to __define this endpoint at the very end of your API__, as it literally accepts every request. ## Exception Handling Grape can be told to rescue all `StandardError` exceptions and return them in the API format. ```ruby class Twitter::API < Grape::API rescue_from :all end ``` This mimics [default `rescue` behaviour](https://ruby-doc.org/core/StandardError.html) when an exception type is not provided. Any other exception should be rescued explicitly, see [below](#exceptions-that-should-be-rescued-explicitly). Grape can also rescue from all exceptions and still use the built-in exception handing. This will give the same behavior as `rescue_from :all` with the addition that Grape will use the exception handling defined by all Exception classes that inherit `Grape::Exceptions::Base`. The intent of this setting is to provide a simple way to cover the most common exceptions and return any unexpected exceptions in the API format. ```ruby class Twitter::API < Grape::API rescue_from :grape_exceptions end ``` If you want to customize the shape of grape exceptions returned to the user, to match your `:all` handler for example, you can pass a block to `rescue_from :grape_exceptions`. ```ruby rescue_from :grape_exceptions do |e| error!(e, e.status) end ``` You can also rescue specific exceptions. ```ruby class Twitter::API < Grape::API rescue_from ArgumentError, UserDefinedError end ``` In this case ```UserDefinedError``` must be inherited from ```StandardError```. Notice that you could combine these two approaches (rescuing custom errors takes precedence). For example, it's useful for handling all exceptions except Grape validation errors. ```ruby class Twitter::API < Grape::API rescue_from Grape::Exceptions::ValidationErrors do |e| error!(e, 400) end rescue_from :all end ``` The error format will match the request format. See "Content-Types" below. Custom error formatters for existing and additional types can be defined with a proc. ```ruby class Twitter::API < Grape::API error_formatter :txt, ->(message, backtrace, options, env, original_exception) { "error: #{message} from #{backtrace}" } end ``` You can also use a module or class. ```ruby module CustomFormatter def self.call(message, backtrace, options, env, original_exception) { message: message, backtrace: backtrace } end end class Twitter::API < Grape::API error_formatter :custom, CustomFormatter end ``` You can rescue all exceptions with a code block. The `error!` wrapper automatically sets the default error code and content-type. ```ruby class Twitter::API < Grape::API rescue_from :all do |e| error!("rescued from #{e.class.name}") end end ``` Optionally, you can set the format, status code and headers. ```ruby class Twitter::API < Grape::API format :json rescue_from :all do |e| error!({ error: 'Server error.' }, 500, { 'Content-Type' => 'text/error' }) end end ``` You can also rescue all exceptions with a code block and handle the Rack response at the lowest level. ```ruby class Twitter::API < Grape::API rescue_from :all do |e| Rack::Response.new([ e.message ], 500, { 'Content-type' => 'text/error' }) end end ``` Or rescue specific exceptions. ```ruby class Twitter::API < Grape::API rescue_from ArgumentError do |e| error!("ArgumentError: #{e.message}") end rescue_from NoMethodError do |e| error!("NoMethodError: #{e.message}") end end ``` By default, `rescue_from` will rescue the exceptions listed and all their subclasses. Assume you have the following exception classes defined. ```ruby module APIErrors class ParentError < StandardError; end class ChildError < ParentError; end end ``` Then the following `rescue_from` clause will rescue exceptions of type `APIErrors::ParentError` and its subclasses (in this case `APIErrors::ChildError`). ```ruby rescue_from APIErrors::ParentError do |e| error!({ error: "#{e.class} error", message: e.message }, e.status) end ``` To only rescue the base exception class, set `rescue_subclasses: false`. The code below will rescue exceptions of type `RuntimeError` but _not_ its subclasses. ```ruby rescue_from RuntimeError, rescue_subclasses: false do |e| error!({ status: e.status, message: e.message, errors: e.errors }, e.status) end ``` Helpers are also available inside `rescue_from`. ```ruby class Twitter::API < Grape::API format :json helpers do def server_error! error!({ error: 'Server error.' }, 500, { 'Content-Type' => 'text/error' }) end end rescue_from :all do |e| server_error! end end ``` The `rescue_from` handler must return a `Rack::Response` object, call `error!`, or raise an exception (either the original exception or another custom one). The exception raised in `rescue_from` will be handled outside Grape. For example, if you mount Grape in Rails, the exception will be handle by [Rails Action Controller](https://guides.rubyonrails.org/action_controller_overview.html#rescue). Alternately, use the `with` option in `rescue_from` to specify a method or a `proc`. ```ruby class Twitter::API < Grape::API format :json helpers do def server_error! error!({ error: 'Server error.' }, 500, { 'Content-Type' => 'text/error' }) end end rescue_from :all, with: :server_error! rescue_from ArgumentError, with: -> { Rack::Response.new('rescued with a method', 400) } end ``` Inside the `rescue_from` block, the environment of the original controller method(`.self` receiver) is accessible through the `#context` method. ```ruby class Twitter::API < Grape::API rescue_from :all do |e| user_id = context.params[:user_id] error!("error for #{user_id}") end end ``` #### Rescuing exceptions inside namespaces You could put `rescue_from` clauses inside a namespace and they will take precedence over ones defined in the root scope: ```ruby class Twitter::API < Grape::API rescue_from ArgumentError do |e| error!("outer") end namespace :statuses do rescue_from ArgumentError do |e| error!("inner") end get do raise ArgumentError.new end end end ``` Here `'inner'` will be result of handling occurred `ArgumentError`. #### Unrescuable Exceptions `Grape::Exceptions::InvalidVersionHeader`, which is raised when the version in the request header doesn't match the currently evaluated version for the endpoint, will _never_ be rescued from a `rescue_from` block (even a `rescue_from :all`) This is because Grape relies on Rack to catch that error and try the next versioned-route for cases where there exist identical Grape endpoints with different versions. #### Exceptions that should be rescued explicitly Any exception that is not subclass of `StandardError` should be rescued explicitly. Usually it is not a case for an application logic as such errors point to problems in Ruby runtime. This is following [standard recommendations for exceptions handling](https://ruby-doc.org/core/Exception.html). ## Logging `Grape::API` provides a `logger` method which by default will return an instance of the `Logger` class from Ruby's standard library. To log messages from within an endpoint, you need to define a helper to make the logger available in the endpoint context. ```ruby class API < Grape::API helpers do def logger API.logger end end post '/statuses' do logger.info "#{current_user} has statused" end end ``` To change the logger level. ```ruby class API < Grape::API self.logger.level = Logger::INFO end ``` You can also set your own logger. ```ruby class MyLogger def warning(message) puts "this is a warning: #{message}" end end class API < Grape::API logger MyLogger.new helpers do def logger API.logger end end get '/statuses' do logger.warning "#{current_user} has statused" end end ``` For similar to Rails request logging try the [grape_logging](https://github.com/aserafin/grape_logging) or [grape-middleware-logger](https://github.com/ridiculous/grape-middleware-logger) gems. ## API Formats Your API can declare which content-types to support by using `content_type`. If you do not specify any, Grape will support _XML_, _JSON_, _BINARY_, and _TXT_ content-types. The default format is `:txt`; you can change this with `default_format`. Essentially, the two APIs below are equivalent. ```ruby class Twitter::API < Grape::API # no content_type declarations, so Grape uses the defaults end class Twitter::API < Grape::API # the following declarations are equivalent to the defaults content_type :xml, 'application/xml' content_type :json, 'application/json' content_type :binary, 'application/octet-stream' content_type :txt, 'text/plain' default_format :txt end ``` If you declare any `content_type` whatsoever, the Grape defaults will be overridden. For example, the following API will only support the `:xml` and `:rss` content-types, but not `:txt`, `:json`, or `:binary`. Importantly, this means the `:txt` default format is not supported! So, make sure to set a new `default_format`. ```ruby class Twitter::API < Grape::API content_type :xml, 'application/xml' content_type :rss, 'application/xml+rss' default_format :xml end ``` Serialization takes place automatically. For example, you do not have to call `to_json` in each JSON API endpoint implementation. The response format (and thus the automatic serialization) is determined in the following order: * Use the file extension, if specified. If the file is .json, choose the JSON format. * Use the value of the `format` parameter in the query string, if specified. * Use the format set by the `format` option, if specified. * Attempt to find an acceptable format from the `Accept` header. * Use the default format, if specified by the `default_format` option. * Default to `:txt`. For example, consider the following API. ```ruby class MultipleFormatAPI < Grape::API content_type :xml, 'application/xml' content_type :json, 'application/json' default_format :json get :hello do { hello: 'world' } end end ``` * `GET /hello` (with an `Accept: */*` header) does not have an extension or a `format` parameter, so it will respond with JSON (the default format). * `GET /hello.xml` has a recognized extension, so it will respond with XML. * `GET /hello?format=xml` has a recognized `format` parameter, so it will respond with XML. * `GET /hello.xml?format=json` has a recognized extension (which takes precedence over the `format` parameter), so it will respond with XML. * `GET /hello.xls` (with an `Accept: */*` header) has an extension, but that extension is not recognized, so it will respond with JSON (the default format). * `GET /hello.xls` with an `Accept: application/xml` header has an unrecognized extension, but the `Accept` header corresponds to a recognized format, so it will respond with XML. * `GET /hello.xls` with an `Accept: text/plain` header has an unrecognized extension *and* an unrecognized `Accept` header, so it will respond with JSON (the default format). You can override this process explicitly by calling `api_format` in the API itself. For example, the following API will let you upload arbitrary files and return their contents as an attachment with the correct MIME type. ```ruby class Twitter::API < Grape::API post 'attachment' do filename = params[:file][:filename] content_type MIME::Types.type_for(filename)[0].to_s api_format :binary # there's no formatter for :binary, data will be returned "as is" header 'Content-Disposition', "attachment; filename*=UTF-8''#{CGI.escape(filename)}" params[:file][:tempfile].read end end ``` You can have your API only respond to a single format with `format`. If you use this, the API will **not** respond to file extensions other than specified in `format`. For example, consider the following API. ```ruby class SingleFormatAPI < Grape::API format :json get :hello do { hello: 'world' } end end ``` * `GET /hello` will respond with JSON. * `GET /hello.json` will respond with JSON. * `GET /hello.xml`, `GET /hello.foobar`, or *any* other extension will respond with an HTTP 404 error code. * `GET /hello?format=xml` will respond with an HTTP 406 error code, because the XML format specified by the request parameter is not supported. * `GET /hello` with an `Accept: application/xml` header will still respond with JSON, since it could not negotiate a recognized content-type from the headers and JSON is the effective default. The formats apply to parsing, too. The following API will only respond to the JSON content-type and will not parse any other input than `application/json`, `application/x-www-form-urlencoded`, `multipart/form-data`, `multipart/related` and `multipart/mixed`. All other requests will fail with an HTTP 406 error code. ```ruby class Twitter::API < Grape::API format :json end ``` When the content-type is omitted, Grape will return a 406 error code unless `default_format` is specified. The following API will try to parse any data without a content-type using a JSON parser. ```ruby class Twitter::API < Grape::API format :json default_format :json end ``` If you combine `format` with `rescue_from :all`, errors will be rendered using the same format. If you do not want this behavior, set the default error formatter with `default_error_formatter`. ```ruby class Twitter::API < Grape::API format :json content_type :txt, 'text/plain' default_error_formatter :txt end ``` Custom formatters for existing and additional types can be defined with a proc. ```ruby class Twitter::API < Grape::API content_type :xls, 'application/vnd.ms-excel' formatter :xls, ->(object, env) { object.to_xls } end ``` You can also use a module or class. ```ruby module XlsFormatter def self.call(object, env) object.to_xls end end class Twitter::API < Grape::API content_type :xls, 'application/vnd.ms-excel' formatter :xls, XlsFormatter end ``` Built-in formatters are the following. * `:json`: use object's `to_json` when available, otherwise call `MultiJson.dump` * `:xml`: use object's `to_xml` when available, usually via `MultiXml` * `:txt`: use object's `to_txt` when available, otherwise `to_s` * `:serializable_hash`: use object's `serializable_hash` when available, otherwise fallback to `:json` * `:binary`: data will be returned "as is" If a body is present in a request to an API, with a Content-Type header value that is of an unsupported type a "415 Unsupported Media Type" error code will be returned by Grape. Response statuses that indicate no content as defined by [Rack](https://github.com/rack) [here](https://github.com/rack/rack/blob/master/lib/rack/utils.rb#L567) will bypass serialization and the body entity - though there should be none - will not be modified. ### JSONP Grape supports JSONP via [Rack::JSONP](https://github.com/rack/rack-contrib), part of the [rack-contrib](https://github.com/rack/rack-contrib) gem. Add `rack-contrib` to your `Gemfile`. ```ruby require 'rack/contrib' class API < Grape::API use Rack::JSONP format :json get '/' do 'Hello World' end end ``` ### CORS Grape supports CORS via [Rack::CORS](https://github.com/cyu/rack-cors), part of the [rack-cors](https://github.com/cyu/rack-cors) gem. Add `rack-cors` to your `Gemfile`, then use the middleware in your config.ru file. ```ruby require 'rack/cors' use Rack::Cors do allow do origins '*' resource '*', headers: :any, methods: :get end end run Twitter::API ``` ## Content-type Content-type is set by the formatter. You can override the content-type of the response at runtime by setting the `Content-Type` header. ```ruby class API < Grape::API get '/home_timeline_js' do content_type 'application/javascript' "var statuses = ...;" end end ``` ## API Data Formats Grape accepts and parses input data sent with the POST and PUT methods as described in the Parameters section above. It also supports custom data formats. You must declare additional content-types via `content_type` and optionally supply a parser via `parser` unless a parser is already available within Grape to enable a custom format. Such a parser can be a function or a class. With a parser, parsed data is available "as-is" in `env['api.request.body']`. Without a parser, data is available "as-is" and in `env['api.request.input']`. The following example is a trivial parser that will assign any input with the "text/custom" content-type to `:value`. The parameter will be available via `params[:value]` inside the API call. ```ruby module CustomParser def self.call(object, env) { value: object.to_s } end end ``` ```ruby content_type :txt, 'text/plain' content_type :custom, 'text/custom' parser :custom, CustomParser put 'value' do params[:value] end ``` You can invoke the above API as follows. ``` curl -X PUT -d 'data' 'http://localhost:9292/value' -H Content-Type:text/custom -v ``` You can disable parsing for a content-type with `nil`. For example, `parser :json, nil` will disable JSON parsing altogether. The request data is then available as-is in `env['api.request.body']`. ## JSON and XML Processors Grape uses `JSON` and `ActiveSupport::XmlMini` for JSON and XML parsing by default. It also detects and supports [multi_json](https://github.com/intridea/multi_json) and [multi_xml](https://github.com/sferik/multi_xml). Adding those gems to your Gemfile and requiring them will enable them and allow you to swap the JSON and XML back-ends. ## RESTful Model Representations Grape supports a range of ways to present your data with some help from a generic `present` method, which accepts two arguments: the object to be presented and the options associated with it. The options hash may include `:with`, which defines the entity to expose. ### Grape Entities Add the [grape-entity](https://github.com/ruby-grape/grape-entity) gem to your Gemfile. Please refer to the [grape-entity documentation](https://github.com/ruby-grape/grape-entity/blob/master/README.md) for more details. The following example exposes statuses. ```ruby module API module Entities class Status < Grape::Entity expose :user_name expose :text, documentation: { type: 'string', desc: 'Status update text.' } expose :ip, if: { type: :full } expose :user_type, :user_id, if: ->(status, options) { status.user.public? } expose :digest do |status, options| Digest::MD5.hexdigest(status.txt) end expose :replies, using: API::Status, as: :replies end end class Statuses < Grape::API version 'v1' desc 'Statuses index' do params: API::Entities::Status.documentation end get '/statuses' do statuses = Status.all type = current_user.admin? ? :full : :default present statuses, with: API::Entities::Status, type: type end end end ``` You can use entity documentation directly in the params block with `using: Entity.documentation`. ```ruby module API class Statuses < Grape::API version 'v1' desc 'Create a status' params do requires :all, except: [:ip], using: API::Entities::Status.documentation.except(:id) end post '/status' do Status.create! params end end end ``` You can present with multiple entities using an optional Symbol argument. ```ruby get '/statuses' do statuses = Status.all.page(1).per(20) present :total_page, 10 present :per_page, 20 present :statuses, statuses, with: API::Entities::Status end ``` The response will be ``` { total_page: 10, per_page: 20, statuses: [] } ``` In addition to separately organizing entities, it may be useful to put them as namespaced classes underneath the model they represent. ```ruby class Status def entity Entity.new(self) end class Entity < Grape::Entity expose :text, :user_id end end ``` If you organize your entities this way, Grape will automatically detect the `Entity` class and use it to present your models. In this example, if you added `present Status.new` to your endpoint, Grape will automatically detect that there is a `Status::Entity` class and use that as the representative entity. This can still be overridden by using the `:with` option or an explicit `represents` call. You can present `hash` with `Grape::Presenters::Presenter` to keep things consistent. ```ruby get '/users' do present { id: 10, name: :dgz }, with: Grape::Presenters::Presenter end ```` The response will be ```ruby { id: 10, name: 'dgz' } ``` It has the same result with ```ruby get '/users' do present :id, 10 present :name, :dgz end ``` ### Hypermedia and Roar You can use [Roar](https://github.com/apotonick/roar) to render HAL or Collection+JSON with the help of [grape-roar](https://github.com/ruby-grape/grape-roar), which defines a custom JSON formatter and enables presenting entities with Grape's `present` keyword. ### Rabl You can use [Rabl](https://github.com/nesquena/rabl) templates with the help of the [grape-rabl](https://github.com/ruby-grape/grape-rabl) gem, which defines a custom Grape Rabl formatter. ### Active Model Serializers You can use [Active Model Serializers](https://github.com/rails-api/active_model_serializers) serializers with the help of the [grape-active_model_serializers](https://github.com/jrhe/grape-active_model_serializers) gem, which defines a custom Grape AMS formatter. ## Sending Raw or No Data In general, use the binary format to send raw data. ```ruby class API < Grape::API get '/file' do content_type 'application/octet-stream' File.binread 'file.bin' end end ``` You can set the response body explicitly with `body`. ```ruby class API < Grape::API get '/' do content_type 'text/plain' body 'Hello World' # return value ignored end end ``` Use `body false` to return `204 No Content` without any data or content-type. If you want to empty the body with an HTTP status code other than `204 No Content`, you can override the status code after specifying `body false` as follows ```ruby class API < Grape::API get '/' do body false status 304 end end ``` You can also set the response to a file with `sendfile`. This works with the [Rack::Sendfile](https://www.rubydoc.info/gems/rack/Rack/Sendfile) middleware to optimally send the file through your web server software. ```ruby class API < Grape::API get '/' do sendfile '/path/to/file' end end ``` To stream a file in chunks use `stream` ```ruby class API < Grape::API get '/' do stream '/path/to/file' end end ``` If you want to stream non-file data use the `stream` method and a `Stream` object. This is an object that responds to `each` and yields for each chunk to send to the client. Each chunk will be sent as it is yielded instead of waiting for all of the content to be available. ```ruby class MyStream def each yield 'part 1' yield 'part 2' yield 'part 3' end end class API < Grape::API get '/' do stream MyStream.new end end ``` ## Authentication ### Basic Auth Grape has built-in Basic authentication (the given `block` is executed in the context of the current `Endpoint`). Authentication applies to the current namespace and any children, but not parents. ```ruby http_basic do |username, password| # verify user's password here # IMPORTANT: make sure you use a comparison method which isn't prone to a timing attack end ``` ### Register custom middleware for authentication Grape can use custom Middleware for authentication. How to implement these Middleware have a look at `Rack::Auth::Basic` or similar implementations. For registering a Middleware you need the following options: * `label` - the name for your authenticator to use it later * `MiddlewareClass` - the MiddlewareClass to use for authentication * `option_lookup_proc` - A Proc with one Argument to lookup the options at runtime (return value is an `Array` as Parameter for the Middleware). Example: ```ruby Grape::Middleware::Auth::Strategies.add(:my_auth, AuthMiddleware, ->(options) { [options[:realm]] } ) auth :my_auth, { realm: 'Test Api'} do |credentials| # lookup the user's password here { 'user1' => 'password1' }[username] end ``` Use [Doorkeeper](https://github.com/doorkeeper-gem/doorkeeper), [warden-oauth2](https://github.com/opperator/warden-oauth2) or [rack-oauth2](https://github.com/nov/rack-oauth2) for OAuth2 support. You can access the controller params, headers, and helpers through the context with the `#context` method inside any auth middleware inherited from `Grape::Middleware::Auth::Base`. ## Describing and Inspecting an API Grape routes can be reflected at runtime. This can notably be useful for generating documentation. Grape exposes arrays of API versions and compiled routes. Each route contains a `prefix`, `version`, `namespace`, `method` and `params`. You can add custom route settings to the route metadata with `route_setting`. ```ruby class TwitterAPI < Grape::API version 'v1' desc 'Includes custom settings.' route_setting :custom, key: 'value' get do end end ``` Examine the routes at runtime. ```ruby TwitterAPI::versions # yields [ 'v1', 'v2' ] TwitterAPI::routes # yields an array of Grape::Route objects TwitterAPI::routes[0].version # => 'v1' TwitterAPI::routes[0].description # => 'Includes custom settings.' TwitterAPI::routes[0].settings[:custom] # => { key: 'value' } ``` Note that `Route#route_xyz` methods have been deprecated since 0.15.0 and removed since 2.0.1. Please use `Route#xyz` instead. Note that difference of `Route#options` and `Route#settings`. The `options` can be referred from your route, it should be set by specifing key and value on verb methods such as `get`, `post` and `put`. The `settings` can also be referred from your route, but it should be set by specifing key and value on `route_setting`. ## Current Route and Endpoint It's possible to retrieve the information about the current route from within an API call with `route`. ```ruby class MyAPI < Grape::API desc 'Returns a description of a parameter.' params do requires :id, type: Integer, desc: 'Identity.' end get 'params/:id' do route.params[params[:id]] # yields the parameter description end end ``` The current endpoint responding to the request is `self` within the API block or `env['api.endpoint']` elsewhere. The endpoint has some interesting properties, such as `source` which gives you access to the original code block of the API implementation. This can be particularly useful for building a logger middleware. ```ruby class ApiLogger < Grape::Middleware::Base def before file = env['api.endpoint'].source.source_location[0] line = env['api.endpoint'].source.source_location[1] logger.debug "[api] #{file}:#{line}" end end ``` ## Before, After and Finally Blocks can be executed before or after every API call, using `before`, `after`, `before_validation` and `after_validation`. If the API fails the `after` call will not be triggered, if you need code to execute for sure use the `finally`. Before and after callbacks execute in the following order: 1. `before` 2. `before_validation` 3. _validations_ 4. `after_validation` (upon successful validation) 5. _the API call_ (upon successful validation) 6. `after` (upon successful validation and API call) 7. `finally` (always) Steps 4, 5 and 6 only happen if validation succeeds. If a request for a resource is made with an unsupported HTTP method (returning HTTP 405) only `before` callbacks will be executed. The remaining callbacks will be bypassed. If a request for a resource is made that triggers the built-in `OPTIONS` handler, only `before` and `after` callbacks will be executed. The remaining callbacks will be bypassed. For example, using a simple `before` block to set a header. ```ruby before do header 'X-Robots-Tag', 'noindex' end ``` You can ensure a block of code runs after every request (including failures) with `finally`: ```ruby finally do # this code will run after every request (successful or failed) end ``` **Namespaces** Callbacks apply to each API call within and below the current namespace: ```ruby class MyAPI < Grape::API get '/' do "root - #{@blah}" end namespace :foo do before do @blah = 'blah' end get '/' do "root - foo - #{@blah}" end namespace :bar do get '/' do "root - foo - bar - #{@blah}" end end end end ``` The behavior is then: ```bash GET / # 'root - ' GET /foo # 'root - foo - blah' GET /foo/bar # 'root - foo - bar - blah' ``` Params on a `namespace` (or whichever alias you are using) will also be available when using `before_validation` or `after_validation`: ```ruby class MyAPI < Grape::API params do requires :blah, type: Integer end resource ':blah' do after_validation do # if we reach this point validations will have passed @blah = declared(params, include_missing: false)[:blah] end get '/' do @blah.class end end end ``` The behavior is then: ```bash GET /123 # 'Integer' GET /foo # 400 error - 'blah is invalid' ``` **Versioning** When a callback is defined within a version block, it's only called for the routes defined in that block. ```ruby class Test < Grape::API resource :foo do version 'v1', :using => :path do before do @output ||= 'v1-' end get '/' do @output += 'hello' end end version 'v2', :using => :path do before do @output ||= 'v2-' end get '/' do @output += 'hello' end end end end ``` The behavior is then: ```bash GET /foo/v1 # 'v1-hello' GET /foo/v2 # 'v2-hello' ``` **Altering Responses** Using `present` in any callback allows you to add data to a response: ```ruby class MyAPI < Grape::API format :json after_validation do present :name, params[:name] if params[:name] end get '/greeting' do present :greeting, 'Hello!' end end ``` The behavior is then: ```bash GET /greeting # {"greeting":"Hello!"} GET /greeting?name=Alan # {"name":"Alan","greeting":"Hello!"} ``` Instead of altering a response, you can also terminate and rewrite it from any callback using `error!`, including `after`. This will cause all subsequent steps in the process to not be called. **This includes the actual api call and any callbacks** ## Anchoring Grape by default anchors all request paths, which means that the request URL should match from start to end to match, otherwise a `404 Not Found` is returned. However, this is sometimes not what you want, because it is not always known upfront what can be expected from the call. This is because Rack-mount by default anchors requests to match from the start to the end, or not at all. Rails solves this problem by using a `anchor: false` option in your routes. In Grape this option can be used as well when a method is defined. For instance when your API needs to get part of an URL, for instance: ```ruby class TwitterAPI < Grape::API namespace :statuses do get '/(*:status)', anchor: false do end end end ``` This will match all paths starting with '/statuses/'. There is one caveat though: the `params[:status]` parameter only holds the first part of the request url. Luckily this can be circumvented by using the described above syntax for path specification and using the `PATH_INFO` Rack environment variable, using `env['PATH_INFO']`. This will hold everything that comes after the '/statuses/' part. ## Instance Variables You can use instance variables to pass information across the various stages of a request. An instance variable set within a `before` validator is accessible within the endpoint's code and can also be utilized within the `rescue_from` handler. ```ruby class TwitterAPI < Grape::API before do @var = 1 end get '/' do puts @var # => 1 raise end rescue_from :all do puts @var # => 1 end end ``` The values of instance variables cannot be shared among various endpoints within the same API. This limitation arises due to Grape generating a new instance for each request made. Consequently, instance variables set within an endpoint during one request differ from those set during a subsequent request, as they exist within separate instances. ```ruby class TwitterAPI < Grape::API get '/first' do @var = 1 puts @var # => 1 end get '/second' do puts @var # => nil end end ``` ## Using Custom Middleware ### Grape Middleware You can make a custom middleware by using `Grape::Middleware::Base`. It's inherited from some grape official middlewares in fact. For example, you can write a middleware to log application exception. ```ruby class LoggingError < Grape::Middleware::Base def after return unless @app_response && @app_response[0] == 500 env['rack.logger'].error("Raised error on #{env['PATH_INFO']}") end end ``` Your middleware can overwrite application response as follows, except error case. ```ruby class Overwriter < Grape::Middleware::Base def after [200, { 'Content-Type' => 'text/plain' }, ['Overwritten.']] end end ``` You can add your custom middleware with `use`, that push the middleware onto the stack, and you can also control where the middleware is inserted using `insert`, `insert_before` and `insert_after`. ```ruby class CustomOverwriter < Grape::Middleware::Base def after [200, { 'Content-Type' => 'text/plain' }, [@options[:message]]] end end class API < Grape::API use Overwriter insert_before Overwriter, CustomOverwriter, message: 'Overwritten again.' insert 0, CustomOverwriter, message: 'Overwrites all other middleware.' get '/' do end end ``` You can access the controller params, headers, and helpers through the context with the `#context` method inside any middleware inherited from `Grape::Middleware::Base`. ### Rails Middleware Note that when you're using Grape mounted on Rails you don't have to use Rails middleware because it's already included into your middleware stack. You only have to implement the helpers to access the specific `env` variable. If you are using a custom application that is inherited from `Rails::Application` and need to insert a new middleware among the ones initiated via Rails, you will need to register it manually in your custom application class. ```ruby class Company::Application < Rails::Application config.middleware.insert_before(Rack::Attack, Middleware::ApiLogger) end ``` ### Remote IP By default you can access remote IP with `request.ip`. This is the remote IP address implemented by Rack. Sometimes it is desirable to get the remote IP [Rails-style](http://stackoverflow.com/questions/10997005/whats-the-difference-between-request-remote-ip-and-request-ip-in-rails) with `ActionDispatch::RemoteIp`. Add `gem 'actionpack'` to your Gemfile and `require 'action_dispatch/middleware/remote_ip.rb'`. Use the middleware in your API and expose a `client_ip` helper. See [this documentation](http://api.rubyonrails.org/classes/ActionDispatch/RemoteIp.html) for additional options. ```ruby class API < Grape::API use ActionDispatch::RemoteIp helpers do def client_ip env['action_dispatch.remote_ip'].to_s end end get :remote_ip do { ip: client_ip } end end ``` ## Writing Tests ### Writing Tests with Rack Use `rack-test` and define your API as `app`. #### RSpec You can test a Grape API with RSpec by making HTTP requests and examining the response. ```ruby describe Twitter::API do include Rack::Test::Methods def app Twitter::API end context 'GET /api/statuses/public_timeline' do it 'returns an empty array of statuses' do get '/api/statuses/public_timeline' expect(last_response.status).to eq(200) expect(JSON.parse(last_response.body)).to eq [] end end context 'GET /api/statuses/:id' do it 'returns a status by id' do status = Status.create! get "/api/statuses/#{status.id}" expect(last_response.body).to eq status.to_json end end end ``` There's no standard way of sending arrays of objects via an HTTP GET, so POST JSON data and specify the correct content-type. ```ruby describe Twitter::API do context 'POST /api/statuses' do it 'creates many statuses' do statuses = [{ text: '...' }, { text: '...'}] post '/api/statuses', statuses.to_json, 'CONTENT_TYPE' => 'application/json' expect(last_response.body).to eq 201 end end end ``` #### Airborne You can test with other RSpec-based frameworks, including [Airborne](https://github.com/brooklynDev/airborne), which uses `rack-test` to make requests. ```ruby require 'airborne' Airborne.configure do |config| config.rack_app = Twitter::API end describe Twitter::API do context 'GET /api/statuses/:id' do it 'returns a status by id' do status = Status.create! get "/api/statuses/#{status.id}" expect_json(status.as_json) end end end ``` #### MiniTest ```ruby require 'test_helper' class Twitter::APITest < MiniTest::Test include Rack::Test::Methods def app Twitter::API end def test_get_api_statuses_public_timeline_returns_an_empty_array_of_statuses get '/api/statuses/public_timeline' assert last_response.ok? assert_equal [], JSON.parse(last_response.body) end def test_get_api_statuses_id_returns_a_status_by_id status = Status.create! get "/api/statuses/#{status.id}" assert_equal status.to_json, last_response.body end end ``` ### Writing Tests with Rails #### RSpec ```ruby describe Twitter::API do context 'GET /api/statuses/public_timeline' do it 'returns an empty array of statuses' do get '/api/statuses/public_timeline' expect(response.status).to eq(200) expect(JSON.parse(response.body)).to eq [] end end context 'GET /api/statuses/:id' do it 'returns a status by id' do status = Status.create! get "/api/statuses/#{status.id}" expect(response.body).to eq status.to_json end end end ``` In Rails, HTTP request tests would go into the `spec/requests` group. You may want your API code to go into `app/api` - you can match that layout under `spec` by adding the following in `spec/rails_helper.rb`. ```ruby RSpec.configure do |config| config.include RSpec::Rails::RequestExampleGroup, type: :request, file_path: /spec\/api/ end ``` #### MiniTest ```ruby class Twitter::APITest < ActiveSupport::TestCase include Rack::Test::Methods def app Rails.application end test 'GET /api/statuses/public_timeline returns an empty array of statuses' do get '/api/statuses/public_timeline' assert last_response.ok? assert_equal [], JSON.parse(last_response.body) end test 'GET /api/statuses/:id returns a status by id' do status = Status.create! get "/api/statuses/#{status.id}" assert_equal status.to_json, last_response.body end end ``` ### Stubbing Helpers Because helpers are mixed in based on the context when an endpoint is defined, it can be difficult to stub or mock them for testing. The `Grape::Endpoint.before_each` method can help by allowing you to define behavior on the endpoint that will run before every request. ```ruby describe 'an endpoint that needs helpers stubbed' do before do Grape::Endpoint.before_each do |endpoint| allow(endpoint).to receive(:helper_name).and_return('desired_value') end end after do Grape::Endpoint.before_each nil end it 'stubs the helper' do end end ``` ## Reloading API Changes in Development ### Reloading in Rack Applications Use [grape-reload](https://github.com/AlexYankee/grape-reload). ### Reloading in Rails Applications Add API paths to `config/application.rb`. ```ruby # Auto-load API and its subdirectories config.paths.add File.join('app', 'api'), glob: File.join('**', '*.rb') config.autoload_paths += Dir[Rails.root.join('app', 'api', '*')] ``` Create `config/initializers/reload_api.rb`. ```ruby if Rails.env.development? ActiveSupport::Dependencies.explicitly_unloadable_constants << 'Twitter::API' api_files = Dir[Rails.root.join('app', 'api', '**', '*.rb')] api_reloader = ActiveSupport::FileUpdateChecker.new(api_files) do Rails.application.reload_routes! end ActionDispatch::Callbacks.to_prepare do api_reloader.execute_if_updated end end ``` For Rails >= 5.1.4, change this: ```ruby ActionDispatch::Callbacks.to_prepare do api_reloader.execute_if_updated end ``` to this: ```ruby ActiveSupport::Reloader.to_prepare do api_reloader.execute_if_updated end ``` See [StackOverflow #3282655](http://stackoverflow.com/questions/3282655/ruby-on-rails-3-reload-lib-directory-for-each-request/4368838#4368838) for more information. ## Performance Monitoring ### Active Support Instrumentation Grape has built-in support for [ActiveSupport::Notifications](http://api.rubyonrails.org/classes/ActiveSupport/Notifications.html) which provides simple hook points to instrument key parts of your application. The following are currently supported: #### endpoint_run.grape The main execution of an endpoint, includes filters and rendering. * *endpoint* - The endpoint instance #### endpoint_render.grape The execution of the main content block of the endpoint. * *endpoint* - The endpoint instance #### endpoint_run_filters.grape * *endpoint* - The endpoint instance * *filters* - The filters being executed * *type* - The type of filters (before, before_validation, after_validation, after) #### endpoint_run_validators.grape The execution of validators. * *endpoint* - The endpoint instance * *validators* - The validators being executed * *request* - The request being validated #### format_response.grape Serialization or template rendering. * *env* - The request environment * *formatter* - The formatter object (e.g., `Grape::Formatter::Json`) See the [ActiveSupport::Notifications documentation](http://api.rubyonrails.org/classes/ActiveSupport/Notifications.html) for information on how to subscribe to these events. ### Monitoring Products Grape integrates with following third-party tools: * **New Relic** - [built-in support](https://docs.newrelic.com/docs/agents/ruby-agent/frameworks/grape-instrumentation) from v3.10.0 of the official [newrelic_rpm](https://github.com/newrelic/rpm) gem, also [newrelic-grape](https://github.com/xinminlabs/newrelic-grape) gem * **Librato Metrics** - [grape-librato](https://github.com/seanmoon/grape-librato) gem * **[Skylight](https://www.skylight.io/)** - [skylight](https://github.com/skylightio/skylight-ruby) gem, [documentation](https://docs.skylight.io/grape/) * **[AppSignal](https://www.appsignal.com)** - [appsignal-ruby](https://github.com/appsignal/appsignal-ruby) gem, [documentation](http://docs.appsignal.com/getting-started/supported-frameworks.html#grape) * **[ElasticAPM](https://www.elastic.co/products/apm)** - [elastic-apm](https://github.com/elastic/apm-agent-ruby) gem, [documentation](https://www.elastic.co/guide/en/apm/agent/ruby/3.x/getting-started-rack.html#getting-started-grape) * **[Datadog APM](https://docs.datadoghq.com/tracing/)** - [ddtrace](https://github.com/datadog/dd-trace-rb) gem, [documentation](https://docs.datadoghq.com/tracing/setup_overview/setup/ruby/#grape) ## Contributing to Grape Grape is work of hundreds of contributors. You're encouraged to submit pull requests, propose features and discuss issues. See [CONTRIBUTING](CONTRIBUTING.md). ## Security See [SECURITY](SECURITY.md) for details. ## License MIT License. See [LICENSE](LICENSE) for details. ## Copyright Copyright (c) 2010-2020 Michael Bleigh, Intridea Inc. and Contributors. ", Assign "at most 3 tags" to the expected json: {"id":"453","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"