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Table of Contents

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 stable release of Grape, v1.5.3. Please read UPGRADING when upgrading from a previous version.

Project Resources

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 for more details.

In 2020, we plan to use the money towards gathering Grape contributors for dinner in New York City.

Installation

Ruby 2.4 or newer is required.

Grape is available as a gem, to install it just install the gem:

gem install grape

If you’re using Bundler, add the gem to Gemfile.

gem 'grape'

Run bundle install.

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 ```

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.

ActiveRecord without Rails

If you want to use ActiveRecord within Grape, you will need to make sure that ActiveRecord’s connection pool is handled correctly.

Rails 4

The easiest way to achieve that is by using ActiveRecord’s ConnectionManagement middleware in your config.ru before mounting Grape, e.g.:

ruby use ActiveRecord::ConnectionAdapters::ConnectionManagement

Rails 5+

Use otr-activerecord as follows:

ruby use OTR::ActiveRecord::ConnectionManagement

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. This may lead to undesirable behavior showing the wrong 404 page from the wrong app.

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 => '/'

Rails < 5.2

Modify application.rb:

ruby config.paths.add File.join('app', 'api'), glob: File.join('**', '*.rb') config.autoload_paths += Dir[Rails.root.join('app', 'api', '*')]

See below for additional code that enables reloading of API changes in development.

Rails 6.0

For Rails versions greater than 6.0.0.beta2, Zeitwerk autoloader is the default for CRuby. By default Zeitwerk 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

Keep in mind such declarations as before/after/rescue_from must be placed before mount in a case where they should 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

mount Twitter::Users mount Twitter::Search 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: mounted { configuration[:entity] || API::Entities::Status }.documentation end params do requires :all, using: mounted { configuration[:entity] || API::Entities::Status }.documentation end get ‘/statuses’ do statuses = Status.all type = current_user.admin? ? :full : :default present statuses, with: mounted { configuration[:entity] || API::Entities::Status }, type: type end end

class V1 < Grape::API version ‘v1’ mount BasicAPI, with: { entity: mounted { configuration[:entity] || API::Enitities::Status } } end

class V2 < Grape::API version ‘v2’ mount BasicAPI, with: { entity: mounted { configuration[:entity] || API::Enitities::V2::Status } } end ```

Versioning

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.

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

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.

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 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']] 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 by default this route
  • failure: (former http_codes) A definition of the used failure HTTP Codes and Entities
  • 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

Configuration

Use Grape.configure to set up global settings at load time. Currently the configurable settings are:

  • param_builder: Sets the Parameter Builder, 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.

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 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.

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": { "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"} } } }

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

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’) # => “” 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, 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. 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' requires :middle_name, type: String, regexp: /w+/, desc: 'Middle name' requires :last_name, type: String, regexp: /w+/, desc: 'Last name' 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+/) do requires :first_name, desc: 'First name' requires :middle_name, desc: 'Middle name' requires :last_name, desc: 'Last name' 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 params or 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 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 in cases where a validation is used more than once.

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

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: /[email protected]+/ 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: /[email protected]+/ 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::Base def validate_param!(attr_name, params) unless params[attr_name] =~ /\A[[:alnum:]]+\z/ fail Grape::Exceptions::Validation, 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::Base def validate_param!(attr_name, params) unless params[attr_name].length <= @option fail Grape::Exceptions::Validation, 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::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 fail Grape::Exceptions::Validation, 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 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

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

ruby params do requires :name, values: { value: -> { (1..10).to_a }, message: 'not in range from 1 to 10' }, default: 5 end

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 capitalized kebab case.
  • In the env collection they appear in all uppercase, in snake case, and prefixed with ‘HTTP_’.

The header name will have been normalized per HTTP standards defined in RFC2616 Section 4.2 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 #useruser.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 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

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

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’ ```

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 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 when an exception type is not provided. Any other exception should be rescued explicitly, see below.

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

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: #ee.message”) end

rescue_from NoMethodError do |e| error!(“NoMethodError: #ee.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.

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.

Rails 3.x

When mounted inside containers, such as Rails 3.x, errors such as “404 Not Found” or “406 Not Acceptable” will likely be handled and rendered by Rails handlers. For instance, accessing a nonexistent route “/api/foo” raises a 404, which inside rails will ultimately be translated to an ActionController::RoutingError, which most likely will get rendered to a HTML error page.

Most APIs will enjoy preventing downstream handlers from handling errors. You may set the :cascade option to false for the entire API or separately on specific version definitions, which will remove the X-Cascade: true header from API responses.

ruby cascade false

ruby version 'v1', using: :header, vendor: 'twitter', cascade: false

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 or 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 specifying env['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 env['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, otherwise call to_s
  • :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 here will bypass serialization and the body entity - though there should be none - will not be modified.

JSONP

Grape supports JSONP via Rack::JSONP, part of the 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, part of the 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 and 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 gem to your Gemfile. Please refer to the grape-entity documentation 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 to render HAL or Collection+JSON with the help of grape-roar, which defines a custom JSON formatter and enables presenting entities with Grape’s present keyword.

Rabl

You can use Rabl templates with the help of the grape-rabl gem, which defines a custom Grape Rabl formatter.

Active Model Serializers

You can use Active Model Serializers serializers with the help of the 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.

You can also set the response to a file with sendfile. This works with the 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 and Digest Auth

Grape has built-in Basic and Digest 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

ruby http_digest({ realm: 'Test Api', opaque: 'app secret' }) do |username| # lookup the user's password here 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, warden-oauth2 or 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 route_prefix, route_version, route_namespace, route_method, route_path and route_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.

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.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.

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.

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 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 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 require ‘spec_helper’

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/#statusstatus.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, 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/#statusstatus.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/#statusstatus.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/#statusstatus.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.

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 for more information.

Performance Monitoring

Active Support Instrumentation

Grape has built-in support for ActiveSupport::Notifications 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 for information on how to subscribe to these events.

Monitoring Products

Grape integrates with following third-party tools:

Contributing to Grape

Grape is work of hundreds of contributors. You’re encouraged to submit pull requests, propose features and discuss issues.

See CONTRIBUTING.

Security

See SECURITY for details.

License

MIT License. See LICENSE for details.

Copyright (c) 2010-2020 Michael Bleigh, Intridea Inc. and Contributors.