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.
You're reading the documentation for the next release of Grape, which should be 3.0.0. The current stable release is 2.4.0.
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Ruby 3.0 or newer is required.
Grape is available as a gem, to install it run:
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.
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
Grape's deprecator will be added to your application's deprecators automatically as :grape, so that your application's configuration can be applied to it.
By default Grape will compile the routes on the first route, but it is possible to pre-load routes using the compile! method.
This can be added to your config.ru (if using rackup), application.rb (if using rails), or any file that loads your server.
The above sample creates a Rack application that can be run from a rackup config.ru file with rackup:
(With pre-loading you can use)
Twitter::API.compile! run Twitter::API
And would respond to the following routes:
GET /api/statuses/public_timeline
GET /api/statuses/home_timeline
GET /api/statuses/:id
POST /api/statuses
PUT /api/statuses/:id
DELETE /api/statuses/:id
Grape will also automatically respond to HEAD and OPTIONS for all GET, and just OPTIONS for all other routes.
Alongside Sinatra (or other frameworks)If you wish to mount Grape alongside another Rack framework such as Sinatra, you can do so easily using Rack::Cascade:
# 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.
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:
mount Twitter::API => '/'
Rails's default autoloader is Zeitwerk. By default, it inflects api as Api instead of API. To make our example work, you need to uncomment the lines at the bottom of config/initializers/inflections.rb, and add API as an acronym:
ActiveSupport::Inflector.inflections(:en) do |inflect| inflect.acronym 'API' end
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.
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.
class Twitter::API < Grape::API mount Twitter::APIv1 => '/v1' end
Declarations as before/after/rescue_from can be placed before or after mount. In any case they will be inherited.
class Twitter::API < Grape::API
before do
header 'X-Base-Header', 'will be defined for all APIs that are mounted below'
end
rescue_from :all do
error!({ "error" => "Internal Server Error" }, 500)
end
mount Twitter::Users
mount Twitter::Search
after do
clean_cache!
end
rescue_from ZeroDivisionError do
error!({ "error" => "Not found" }, 404)
end
end
You can mount the same endpoints in two different locations.
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.
You can configure remountable endpoints to change how they behave according to where they are mounted.
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:
# 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.
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)
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.
class ExpressionEndpointAPI < Grape::API
get(mounted { configuration[:route_name] || 'default_name' }) do
# some logic
end
end
class BasicAPI < Grape::API
desc 'Statuses index' do
params: (configuration[:entity] || API::Entities::Status).documentation
end
params do
requires :all, using: (configuration[:entity] || API::Entities::Status).documentation
end
get '/statuses' do
statuses = Status.all
type = current_user.admin? ? :full : :default
present statuses, with: (configuration[:entity] || API::Entities::Status), type: type
end
end
class V1 < Grape::API
version 'v1'
mount BasicAPI, with: { entity: mounted { configuration[:entity] || API::Entities::Status } }
end
class V2 < Grape::API
version 'v2'
mount BasicAPI, with: { entity: mounted { configuration[:entity] || API::Entities::V2::Status } }
end
You have the option to provide various versions of your API by establishing a separate Grape::API class for each offered version and then integrating them into a primary Grape::API class. Ensure that newer versions are mounted before older ones. The default approach to versioning directs the request to the subsequent Rack middleware if a specific version is not found.
require 'v1' require 'v2' require 'v3' class App < Grape::API mount V3 mount V2 mount V1 end
To maintain the same endpoints from earlier API versions without rewriting them, you can indicate multiple versions within the previous API versions.
class V1 < Grape::API
version 'v1', 'v2', 'v3'
get '/foo' do
# your code for GET /foo
end
get '/other' do
# your code for GET /other
end
end
class V2 < Grape::API
version 'v2', 'v3'
get '/var' do
# your code for GET /var
end
end
class V3 < Grape::API
version 'v3'
get '/foo' do
# your new code for GET /foo
end
end
Using the example provided, the subsequent endpoints will be accessible across various versions:
GET /v1/foo GET /v1/other GET /v2/foo # => Same behavior as v1 GET /v2/other # => Same behavior as v1 GET /v2/var # => New endpoint not available in v1 GET /v3/foo # => Different behavior to v1 and v2 GET /v3/other # => Same behavior as v1 and v2 GET /v3/var # => Same behavior as v2
There are four strategies in which clients can reach your API's endpoints: :path, :header, :accept_version_header and :param. The default strategy is :path.
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
version 'v1', using: :header, vendor: 'twitter'
Currently, Grape only supports versioned media types in the following format:
vnd.vendor-and-or-resource-v1234+format
Basically all tokens between the final - and the + will be interpreted as the version.
Using this versioning strategy, clients should pass the desired version in the HTTP Accept head.
curl -H Accept:application/vnd.twitter-v1+json http://localhost:9292/statuses/public_timeline
By default, the first matching version is used when no Accept header is supplied. This behavior is similar to routing in Rails. To circumvent this default behavior, one could use the :strict option. When this option is set to true, a 406 Not Acceptable error is returned when no correct Accept header is supplied.
When an invalid Accept header is supplied, a 406 Not Acceptable error is returned if the :cascade option is set to false. Otherwise a 404 Not Found error is returned by Rack if no other route matches.
Grape will evaluate the relative quality preference included in Accept headers and default to a quality of 1.0 when omitted. In the following example a Grape API that supports XML and JSON in that order will return JSON:
curl -H "Accept: text/xml;q=0.8, application/json;q=0.9" localhost:1234/resource
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.
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.
version 'v1', using: :param, parameter: 'v'
curl http://localhost:9292/statuses/public_timeline?v=v1
You can check whether your API is in conformance with the Rack's specification by calling lint! at the API level or through configuration.
class Api < Grape::API lint! end
Grape.configure do |config| config.lint = true endBug in Rack::ETag under Rack 3.X
If you're using Rack 3.X and the Rack::Etag middleware (used by Rails), a bug related to linting has been fixed in 3.1.13 and 3.0.15 respectively.
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.
desc 'Returns your public timeline.' do
summary 'summary'
detail 'more details'
params API::Entities::Status.documentation
success API::Entities::Entity
failure [[401, 'Unauthorized', 'Entities::Error']]
default { code: 500, message: 'InvalidRequest', model: Entities::Error }
named 'My named route'
headers XAuthToken: {
description: 'Validates your identity',
required: true
},
XOptionalHeader: {
description: 'Not really needed',
required: false
}
hidden false
deprecated false
is_array true
nickname 'nickname'
produces ['application/json']
consumes ['application/json']
tags ['tag1', 'tag2']
end
get :public_timeline do
Status.limit(20)
end
detail: A more enhanced descriptionparams: Define parameters directly from an Entitysuccess: (former entity) The Entity to be used to present the success response for this route.failure: (former http_codes) A definition of the used failure HTTP Codes and Entities.default: The definition and Entity used to present the default response for this route.named: A helper to give a route a name and find it with this name in the documentation Hashheaders: A definition of the used HeadersUse 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
Grape.configure do |config| config.setting = value end
For example, for the param_builder, the following code could run in an initializer:
Grape.configure do |config| config.param_builder = :hashie_mash end
Available parameter builders are :hash, :hash_with_indifferent_access, and :hashie_mash. See params_builder.
You can also configure a single API:
API.configure do |config| config[key] = value end
This will be available inside the API with configuration, as if it were mount configuration.
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.
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:
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:
post 'upload' do # file in params[:image_file] end
In the case of conflict between either of:
GET, POST and PUT parametersPOST and PUTRoute string parameters will have precedence.
By default parameters are available as ActiveSupport::HashWithIndifferentAccess. This can be changed to, for example, Ruby Hash or Hashie::Mash for the entire API.
class API < Grape::API
build_with :hashie_mash
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.
params do build_with :hash optional :color, type: String end
In the example above, params["color"] will return nil since params is a plain Hash.
Available parameter builders are :hash, :hash_with_indifferent_access, and :hashie_mash. See params_builder.
Grape allows you to access only the parameters that have been declared by your params block. It will:
Consider the following API endpoint:
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
curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{"user": {"first_name":"first name", "last_name": "last name"}}'
Response
{
"declared_params": {}
}
Once we add parameters requirements, grape will start returning only the declared parameters.
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
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
{
"declared_params": {
"user": {
"first_name": "first name",
"last_name": "last name"
}
}
}
Missing params that are declared as type Hash or Array will be included.
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
curl -X POST -H "Content-Type: application/json" localhost:9292/users/signup -d '{}'
Response
{
"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.
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.
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
curl -X GET -H "Content-Type: application/json" localhost:9292/parent/foo/bar
Response
{
"without_parent_namespaces": {
"child_name": "bar"
},
"with_parent_namespaces": {
"parent_name": "foo",
"child_name": "bar"
},
}
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:
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
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
{
"declared_params": {
"user": {
"first_name": "first name"
}
}
}
Response with include_missing:true
{
"declared_params": {
"user": {
"first_name": "first name",
"last_name": null
}
}
}
It also works on nested hashes:
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
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
{
"declared_params": {
"user": {
"first_name": "first name",
"address": {
"city": "SF"
}
}
}
}
Response with include_missing:true
{
"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
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
{
"declared_params": {
"user": {
"first_name": "first name",
"last_name": null,
"address": { "city": "SF"}
}
}
}
By default declared(params) will not evaluate given and return all parameters. Use evaluate_given to evaluate all given blocks and return only parameters that satisfy given conditions. Consider the following API:
format :json
params do
optional :child_id, type: Integer
given :child_id do
requires :father_id, type: Integer
end
end
post 'child' do
{ 'declared_params' => declared(params, evaluate_given: true) }
end
Request
curl -X POST -H "Content-Type: application/json" localhost:9292/child -d '{"father_id": 1}'
Response with evaluate_given:false
{
"declared_params": {
"child_id": null,
"father_id": 1
}
}
Response with evaluate_given:true
{
"declared_params": {
"child_id": null
}
}
It also works on nested hashes:
format :json
params do
requires :child, type: Hash do
optional :child_id, type: Integer
given :child_id do
requires :father_id, type: Integer
end
end
end
post 'child' do
{ 'declared_params' => declared(params, evaluate_given: true) }
end
Request
curl -X POST -H "Content-Type: application/json" localhost:9292/child -d '{"child": {"father_id": 1}}'
Response with evaluate_given:false
{
"declared_params": {
"child": {
"child_id": null,
"father_id": 1
}
}
}
Response with evaluate_given:true
{
"declared_params": {
"child": {
"child_id": null
}
}
}
Using route_param takes higher precedence over a regular parameter defined with same name:
params do
requires :foo, type: String
end
route_param :foo do
get do
{ value: params[:foo] }
end
end
Request
curl -X POST -H "Content-Type: application/json" localhost:9292/bar -d '{"foo": "baz"}'
Response
Parameter Validation and CoercionYou can define validations and coercion options for your parameters using a params block.
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.
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.
params do optional :color, type: String, default: 'blue', values: ['red', 'green'] end
The correct implementation is to ensure the default value passes all validations.
params do optional :color, type: String, default: 'blue', values: ['blue', 'red', 'green'] end
You can use the value of one parameter as the default value of some other parameter. In this case, if the primary_color parameter is not provided, it will have the same value as the color one. If both of them not provided, both of them will have blue value.
params do
optional :color, type: String, default: 'blue'
optional :primary_color, type: String, default: -> (params) { params[:color] }
end Supported Parameter Types
The following are all valid types, supported out of the box by Grape:
File)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.
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.
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.
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.
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.
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:
params do requires :avatar, type: File end post '/' do params[:avatar][:filename] # => 'avatar.png' params[:avatar][:type] # => 'image/png' params[:avatar][:tempfile] # => #<File> end
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:
params do
requires :json, type: JSON do
requires :int, type: Integer, values: [1, 2, 3]
end
end
get '/' do
params[:json].inspect
end
client.get('/', json: '{"int":1}') # => "{:int=>1}"
client.get('/', json: '[{"int":"1"}]') # => "[{:int=>1}]"
client.get('/', json: '{"int":4}') # => HTTP 400
client.get('/', json: '[{"int":4}]') # => HTTP 400
Additionally type: Array[JSON] may be used, which explicitly marks the parameter as an array of objects. If a single object is supplied it will be wrapped.
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.
Variant-type parameters can be declared using the types option rather than type:
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:
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.
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
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:
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:
params do
optional :category
given category: ->(val) { val == 'foo' } do
requires :description
end
end
You can rename parameters:
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.
Parameters options can be grouped. It can be useful if you want to extract common validation or types for several parameters. Within these groups, individual parameters can extend or selectively override the common settings, allowing you to maintain the defaults at the group level while still applying parameter-specific rules where necessary.
The example below presents a typical case when parameters share common options.
params do
requires :first_name, type: String, regexp: /w+/, desc: 'First name', documentation: { in: 'body' }
optional :middle_name, type: String, regexp: /w+/, desc: 'Middle name', documentation: { in: 'body', x: { nullable: true } }
requires :last_name, type: String, regexp: /w+/, desc: 'Last name', documentation: { in: 'body' }
end
Grape allows you to present the same logic through the with method in your parameters block, like so:
params do
with(type: String, regexp: /w+/, documentation: { in: 'body' }) do
requires :first_name, desc: 'First name'
optional :middle_name, desc: 'Middle name', documentation: { x: { nullable: true } }
requires :last_name, desc: 'Last name'
end
end
You can organize settings into layers using nested `with' blocks. Each layer can use, add to, or change the settings of the layer above it. This helps to keep complex parameters organized and consistent, while still allowing for specific customizations to be made.
params do
with(documentation: { in: 'body' }) do # Applies documentation to all nested parameters
with(type: String, regexp: /\w+/) do # Applies type and validation to names
requires :first_name, desc: 'First name'
requires :last_name, desc: 'Last name'
end
optional :age, type: Integer, desc: 'Age', documentation: { x: { nullable: true } } # Specific settings for 'age'
end
end
You can rename parameters using as, which can be useful when refactoring existing APIs:
resource :users do
params do
requires :email_address, as: :email
requires :password
end
post do
User.create!(declared(params)) # User takes email and password
end
end
The value passed to as will be the key when calling declared(params).
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.
params do requires :username, allow_blank: false optional :first_name, allow_blank: false end
Parameters can be restricted to a specific set of values with the :values option.
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?).
params do requires :latitude, type: Float, values: -90.0..+90.0 requires :longitude, type: Float, values: -180.0..+180.0 optional :letters, type: Array[String], values: 'a'..'z' end
Note endless ranges are also supported with ActiveSupport >= 6.0, but they require that the type be provided.
params do requires :minimum, type: Integer, values: 10.. optional :maximum, type: Integer, values: ..10 end
Note that both range endpoints have to be a #kind_of? your :type option (if you don't supply the :type option, it will be guessed to be equal to the class of the range's first endpoint). So the following is invalid:
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.
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.
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.
Note that allow_blank validator applies while using :values. In the following example the absence of :allow_blank does not prevent :state from receiving blank values because :allow_blank defaults to true.
params do requires :state, type: Symbol, values: [:active, :inactive] end
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.
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
A same_as option can be given to ensure that values of parameters match.
params do requires :password requires :password_confirmation, same_as: :password end
Parameters with types that support #length method can be restricted to have a specific length with the :length option.
The validator accepts :min or :max or both options or only :is to validate that the value of the parameter is within the given limits.
params do
requires :code, type: String, length: { is: 2 }
requires :str, type: String, length: { min: 3 }
requires :list, type: [Integer], length: { min: 3, max: 5 }
requires :hash, type: Hash, length: { max: 5 }
end
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.
params do requires :email, regexp: /.+@.+/ end
The validator will pass if the parameter was sent without value. To ensure that the parameter contains a value, use allow_blank: false.
params do requires :email, allow_blank: false, regexp: /.+@.+/ end
Parameters can be defined as mutually_exclusive, ensuring that they aren't present at the same time in a request.
params do optional :beer optional :wine mutually_exclusive :beer, :wine end
Multiple sets can be defined:
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.
Parameters can be defined as 'exactly_one_of', ensuring that exactly one parameter gets selected.
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.
Parameters can be defined as 'at_least_one_of', ensuring that at least one parameter gets selected.
params do optional :beer optional :wine optional :juice at_least_one_of :beer, :wine, :juice end
Parameters can be defined as 'all_or_none_of', ensuring that all or none of parameters gets selected.
params do optional :beer optional :wine optional :juice all_or_none_of :beer, :wine, :juice endNested
mutually_exclusive, exactly_one_of, at_least_one_of, all_or_none_of
All of these methods can be used at any nested level.
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.
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.
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.
namespace :arithmetic do
route_param :n, type: Integer do
desc 'Returns in power'
get 'power' do
params[:n] ** params[:n]
end
end
end
class AlphaNumeric < Grape::Validations::Validators::Base
def validate_param!(attr_name, params)
unless params[attr_name] =~ /\A[[:alnum:]]+\z/
raise Grape::Exceptions::Validation.new params: [@scope.full_name(attr_name)], message: 'must consist of alpha-numeric characters'
end
end
end
params do requires :text, alpha_numeric: true end
You can also create custom classes that take parameters.
class Length < Grape::Validations::Validators::Base
def validate_param!(attr_name, params)
unless params[attr_name].length <= @option
raise Grape::Exceptions::Validation.new params: [@scope.full_name(attr_name)], message: "must be at the most #{@option} characters long"
end
end
end
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.
class Admin < Grape::Validations::Validators::Base
def validate(request)
# return if the param we are checking was not in request
# @attrs is a list containing the attribute we are currently validating
# in our sample case this method once will get called with
# @attrs being [:admin_field] and once with @attrs being [:admin_false_field]
return unless request.params.key?(@attrs.first)
# check if admin flag is set to true
return unless @option
# check if user is admin or not
# as an example get a token from request and check if it's admin or not
raise Grape::Exceptions::Validation.new params: @attrs, message: 'Can not set admin-only field.' unless request.headers['X-Access-Token'] == 'admin'
end
end
And use it in your endpoint definition as:
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 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.
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"]}].
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.
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.
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.
params do required :blah, allow_blank: false, regexp: /blah/, fail_fast: true end
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 messagesGrape supports custom validation messages for parameter-related and coerce-related error messages.
presence, allow_blank, values, regexp
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
params do
requires :password
requires :password_confirmation, same_as: { value: :password, message: 'not match' }
end
params do
requires :code, type: String, length: { is: 2, message: 'code is expected to be exactly 2 characters long' }
requires :str, type: String, length: { min: 5, message: 'str is expected to be at least 5 characters long' }
requires :list, type: [Integer], length: { min: 2, max: 3, message: 'list is expected to have between 2 and 3 elements' }
end
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
params do optional :beer optional :wine optional :juice mutually_exclusive :beer, :wine, :juice, message: "are mutually exclusive cannot pass both params" end
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
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
params do
requires :int, type: { value: Integer, message: "type cast is invalid" }
end
params do
requires :name, values: { value: -> { (1..10).to_a }, message: 'not in range from 1 to 10' }
endPass symbols for i18n translations
You can pass a symbol if you want i18n translations for your custom validation messages.
params do requires :name, message: :name_required end
# en.yml
en:
grape:
errors:
format: ! '%{attributes} %{message}'
messages:
name_required: 'must be present' Overriding Attribute Names
You can also override attribute names.
# 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'
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
params do
requires :name, values: { value: -> { (1..10).to_a }, message: 'not in range from 1 to 10' }, default: 5
end Using dry-validation or dry-schema
As an alternative to the params DSL described above, you can use a schema or dry-validation contract to describe an endpoint's parameters. This can be especially useful if you use the above already in some other parts of your application. If not, you'll need to add dry-validation or dry-schema to your Gemfile.
Then call contract with a contract or schema defined previously:
CreateOrdersSchema = Dry::Schema.Params do
required(:orders).array(:hash) do
required(:name).filled(:string)
optional(:volume).maybe(:integer, lt?: 9)
end
end
# ...
contract CreateOrdersSchema
or with a block, using the schema definition syntax:
contract do
required(:orders).array(:hash) do
required(:name).filled(:string)
optional(:volume).maybe(:integer, lt?: 9)
end
end
The latter will define a coercing schema (Dry::Schema.Params). When using the former approach, it's up to you to decide whether the input will need coercing.
The params and contract declarations can also be used together in the same API, e.g. to describe different parts of a nested namespace for an endpoint.
Request headers are available through the headers helper or from env in their original form.
get do
error!('Unauthorized', 401) unless headers['Secret-Password'] == 'swordfish'
end
get do
error!('Unauthorized', 401) unless env['HTTP_SECRET_PASSWORD'] == 'swordfish'
end
The above example may have been requested as follows:
curl -H "secret_PassWord: swordfish" ...
The header name will have been normalized for you.
header helper names will be coerced into a downcased kebab case as secret-password if using Rack 3.header helper names will be coerced into a capitalized kebab case as Secret-PassWord if using Rack < 3.env collection they appear in all uppercase, in snake case, and prefixed with 'HTTP_' as HTTP_SECRET_PASSWORDThe header name will have been normalized per HTTP standards defined in RFC2616 Section 4.2 regardless of what is being sent by a client.
You can set a response header with header inside an API.
header 'X-Robots-Tag', 'noindex'
When raising error!, pass additional headers as arguments. Additional headers will be merged with headers set before error! call.
error! 'Unauthorized', 401, 'X-Error-Detail' => 'Invalid token.'
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.
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.
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.
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
You can define helper methods that your endpoints can use with the helpers macro by either giving a block or an array of modules.
module StatusHelpers
def user_info(user)
"#{user} has statused #{user.statuses} status(s)"
end
end
module HttpCodesHelpers
def unauthorized
401
end
end
class API < Grape::API
# define helpers with a block
helpers do
def current_user
User.find(params[:user_id])
end
end
# or mix in an array of modules
helpers StatusHelpers, HttpCodesHelpers
before do
error!('Access Denied', unauthorized) unless current_user
end
get 'info' do
# helpers available in your endpoint and filters
user_info(current_user)
end
end
You can define reusable params using helpers.
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.
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.
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
If you need methods for generating paths inside your endpoints, please see the grape-route-helpers gem.
You can attach additional documentation to params using a documentation hash.
params do
optional :first_name, type: String, documentation: { example: 'Jim' }
requires :last_name, type: String, documentation: { example: 'Smith' }
end
If documentation isn't needed (for instance, it is an internal API), documentation can be disabled.
class API < Grape::API do_not_document! # endpoints... end
In this case, Grape won't create objects related to documentation which are retained in RAM forever.
You can set, get and delete your cookies very simply using cookies method.
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.
cookies[:status_count] = {
value: 0,
expires: Time.tomorrow,
domain: '.twitter.com',
path: '/'
}
cookies[:status_count][:value] +=1
Delete a cookie with delete.
cookies.delete :status_count
Specify an optional path.
cookies.delete :status_count, path: '/'
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
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
post do status :no_content end
You can redirect to a new url temporarily (302) or permanently (301).
redirect '/statuses', permanent: true
You can recognize the endpoint matched with given path.
This API returns an instance of Grape::Endpoint.
class API < Grape::API get '/statuses' do end end API.recognize_path '/statuses'
Since version 2.1.0, the recognize_path method takes into account the parameters type to determine which endpoint should match with given path.
class Books < Grape::API
resource :books do
route_param :id, type: Integer do
# GET /books/:id
get do
#...
end
end
resource :share do
# POST /books/share
post do
# ....
end
end
end
end
API.recognize_path '/books/1' # => /books/:id
API.recognize_path '/books/share' # => /books/share
API.recognize_path '/books/other' # => nil
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!.
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.
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
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.
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
You can abort the execution of an API method by raising errors with error!.
error! 'Access Denied', 401
Anything that responds to #to_s can be given as a first argument to error!.
You can also return JSON formatted objects by raising error! and passing a hash instead of a message.
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.
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.
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.
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.
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.
class API < Grape::API
default_error_status 400
get '/example' do
error! 'This should have http status code 400'
end
end
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:
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.
Grape can be told to rescue all StandardError exceptions and return them in the API format.
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.
class Twitter::API < Grape::API rescue_from :grape_exceptions end
If you want to customize the shape of grape exceptions returned to the user, to match your :all handler for example, you can pass a block to rescue_from :grape_exceptions.
rescue_from :grape_exceptions do |e| error!(e, e.status) end
You can also rescue specific exceptions.
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.
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.
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.
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.
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.
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.
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.
class Twitter::API < Grape::API
rescue_from ArgumentError do |e|
error!("ArgumentError: #{e.message}")
end
rescue_from NoMethodError do |e|
error!("NoMethodError: #{e.message}")
end
end
By default, rescue_from will rescue the exceptions listed and all their subclasses.
Assume you have the following exception classes defined.
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).
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.
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.
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.
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.
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:
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.
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.
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.
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.
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.
class API < Grape::API self.logger.level = Logger::INFO end
You can also set your own logger.
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.
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.
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.
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:
format parameter in the query string, if specified.format option, if specified.Accept header.default_format option.:txt.For example, consider the following API.
class MultipleFormatAPI < Grape::API
content_type :xml, 'application/xml'
content_type :json, 'application/json'
default_format :json
get :hello do
{ hello: 'world' }
end
end
GET /hello (with an Accept: */* header) does not have an extension or a format parameter, so it will respond with JSON (the default format).GET /hello.xml has a recognized extension, so it will respond with XML.GET /hello?format=xml has a recognized format parameter, so it will respond with XML.GET /hello.xml?format=json has a recognized extension (which takes precedence over the format parameter), so it will respond with XML.GET /hello.xls (with an Accept: */* header) has an extension, but that extension is not recognized, so it will respond with JSON (the default format).GET /hello.xls with an Accept: application/xml header has an unrecognized extension, but the Accept header corresponds to a recognized format, so it will respond with XML.GET /hello.xls with an Accept: text/plain header has an unrecognized extension and an unrecognized Accept header, so it will respond with JSON (the default format).You can override this process explicitly by calling api_format in the API itself. For example, the following API will let you upload arbitrary files and return their contents as an attachment with the correct MIME type.
class Twitter::API < Grape::API
post 'attachment' do
filename = params[:file][:filename]
content_type MIME::Types.type_for(filename)[0].to_s
api_format :binary # there's no formatter for :binary, data will be returned "as is"
header 'Content-Disposition', "attachment; filename*=UTF-8''#{CGI.escape(filename)}"
params[:file][:tempfile].read
end
end
You can have your API only respond to a single format with format. If you use this, the API will not respond to file extensions other than specified in format. For example, consider the following API.
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.
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.
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.
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.
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.
module XlsFormatter
def self.call(object, env)
object.to_xls
end
end
class Twitter::API < Grape::API
content_type :xls, 'application/vnd.ms-excel'
formatter :xls, XlsFormatter
end
Built-in formatters are the following.
:json: use object's to_json when available, otherwise call MultiJson.dump:xml: use object's to_xml when available, usually via MultiXml:txt: use object's to_txt when available, otherwise to_s:serializable_hash: use object's serializable_hash when available, otherwise fallback to :json:binary: data will be returned "as is"If a body is present in a request to an API, with a Content-Type header value that is of an unsupported type a "415 Unsupported Media Type" error code will be returned by Grape.
Response statuses that indicate no content as defined by Rack here will bypass serialization and the body entity - though there should be none - will not be modified.
Grape supports JSONP via Rack::JSONP, part of the rack-contrib gem. Add rack-contrib to your Gemfile.
require 'rack/contrib'
class API < Grape::API
use Rack::JSONP
format :json
get '/' do
'Hello World'
end
end
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.
require 'rack/cors'
use Rack::Cors do
allow do
origins '*'
resource '*', headers: :any, methods: :get
end
end
run Twitter::API
Content-type is set by the formatter. You can override the content-type of the response at runtime by setting the Content-Type header.
class API < Grape::API
get '/home_timeline_js' do
content_type 'application/javascript'
"var statuses = ...;"
end
end
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.
module CustomParser
def self.call(object, env)
{ value: object.to_s }
end
end
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'].
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.
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.
Add the grape-entity gem to your Gemfile. Please refer to the grape-entity documentation for more details.
The following example exposes statuses.
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.
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.
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.
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.
get '/users' do
present { id: 10, name: :dgz }, with: Grape::Presenters::Presenter
end
The response will be
It has the same result with
get '/users' do present :id, 10 present :name, :dgz end
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.
You can use Rabl templates with the help of the grape-rabl gem, which defines a custom Grape Rabl formatter.
You can use Active Model Serializers serializers with the help of the grape-active_model_serializers gem, which defines a custom Grape AMS formatter.
In general, use the binary format to send raw data.
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.
class API < Grape::API
get '/' do
content_type 'text/plain'
body 'Hello World'
# return value ignored
end
end
Use body false to return 204 No Content without any data or content-type.
If you want to empty the body with an HTTP status code other than 204 No Content, you can override the status code after specifying body false as follows
class API < Grape::API
get '/' do
body false
status 304
end
end
You can also set the response to a file with sendfile. This works with the Rack::Sendfile middleware to optimally send the file through your web server software.
class API < Grape::API
get '/' do
sendfile '/path/to/file'
end
end
To stream a file in chunks use stream
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.
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
Grape has built-in Basic authentication (the given block is executed in the context of the current Endpoint). Authentication applies to the current namespace and any children, but not parents.
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 endRegister 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 laterMiddlewareClass - the MiddlewareClass to use for authenticationoption_lookup_proc - A Proc with one Argument to lookup the options at runtime (return value is an Array as Parameter for the Middleware).Example:
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.
Grape routes can be reflected at runtime. This can notably be useful for generating documentation.
Grape exposes arrays of API versions and compiled routes. Each route contains a prefix, version, namespace, method and params. You can add custom route settings to the route metadata with route_setting.
class TwitterAPI < Grape::API version 'v1' desc 'Includes custom settings.' route_setting :custom, key: 'value' get do end end
Examine the routes at runtime.
TwitterAPI::versions # yields [ 'v1', 'v2' ]
TwitterAPI::routes # yields an array of Grape::Route objects
TwitterAPI::routes[0].version # => 'v1'
TwitterAPI::routes[0].description # => 'Includes custom settings.'
TwitterAPI::routes[0].settings[:custom] # => { key: 'value' }
Note that Route#route_xyz methods have been deprecated since 0.15.0 and removed since 2.0.1.
Please use Route#xyz instead.
Note that difference of Route#options and Route#settings.
The options can be referred from your route, it should be set by specifying 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 specifying key and value on route_setting.
It's possible to retrieve the information about the current route from within an API call with route.
class MyAPI < Grape::API
desc 'Returns a description of a parameter.'
params do
requires :id, type: Integer, desc: 'Identity.'
end
get 'params/:id' do
route.params[params[:id]] # yields the parameter description
end
end
The current endpoint responding to the request is self within the API block or env['api.endpoint'] elsewhere. The endpoint has some interesting properties, such as source which gives you access to the original code block of the API implementation. This can be particularly useful for building a logger middleware.
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:
beforebefore_validationafter_validation (upon successful validation)after (upon successful validation and API call)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.
before do header 'X-Robots-Tag', 'noindex' end
You can ensure a block of code runs after every request (including failures) with finally:
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:
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:
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:
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:
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.
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:
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:
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:
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
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:
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.
You can use instance variables to pass information across the various stages of a request. An instance variable set within a before validator is accessible within the endpoint's code and can also be utilized within the rescue_from handler.
class TwitterAPI < Grape::API
before do
@var = 1
end
get '/' do
puts @var # => 1
raise
end
rescue_from :all do
puts @var # => 1
end
end
The values of instance variables cannot be shared among various endpoints within the same API. This limitation arises due to Grape generating a new instance for each request made. Consequently, instance variables set within an endpoint during one request differ from those set during a subsequent request, as they exist within separate instances.
class TwitterAPI < Grape::API
get '/first' do
@var = 1
puts @var # => 1
end
get '/second' do
puts @var # => nil
end
end
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.
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.
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.
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.
Note that when you're using Grape mounted on Rails you don't have to use Rails middleware because it's already included into your middleware stack. You only have to implement the helpers to access the specific env variable.
If you are using a custom application that is inherited from Rails::Application and need to insert a new middleware among the ones initiated via Rails, you will need to register it manually in your custom application class.
class Company::Application < Rails::Application config.middleware.insert_before(Rack::Attack, Middleware::ApiLogger) end
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.
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
Use rack-test and define your API as app.
You can test a Grape API with RSpec by making HTTP requests and examining the response.
describe Twitter::API do
include Rack::Test::Methods
def app
Twitter::API
end
context 'GET /api/statuses/public_timeline' do
it 'returns an empty array of statuses' do
get '/api/statuses/public_timeline'
expect(last_response.status).to eq(200)
expect(JSON.parse(last_response.body)).to eq []
end
end
context 'GET /api/statuses/:id' do
it 'returns a status by id' do
status = Status.create!
get "/api/statuses/#{status.id}"
expect(last_response.body).to eq status.to_json
end
end
end
There's no standard way of sending arrays of objects via an HTTP GET, so POST JSON data and specify the correct content-type.
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
You can test with other RSpec-based frameworks, including Airborne, which uses rack-test to make requests.
require 'airborne'
Airborne.configure do |config|
config.rack_app = Twitter::API
end
describe Twitter::API do
context 'GET /api/statuses/:id' do
it 'returns a status by id' do
status = Status.create!
get "/api/statuses/#{status.id}"
expect_json(status.as_json)
end
end
end
require 'test_helper'
class Twitter::APITest < MiniTest::Test
include Rack::Test::Methods
def app
Twitter::API
end
def test_get_api_statuses_public_timeline_returns_an_empty_array_of_statuses
get '/api/statuses/public_timeline'
assert last_response.ok?
assert_equal [], JSON.parse(last_response.body)
end
def test_get_api_statuses_id_returns_a_status_by_id
status = Status.create!
get "/api/statuses/#{status.id}"
assert_equal status.to_json, last_response.body
end
end
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.
RSpec.configure do |config| config.include RSpec::Rails::RequestExampleGroup, type: :request, file_path: /spec\/api/ end
class Twitter::APITest < ActiveSupport::TestCase
include Rack::Test::Methods
def app
Rails.application
end
test 'GET /api/statuses/public_timeline returns an empty array of statuses' do
get '/api/statuses/public_timeline'
assert last_response.ok?
assert_equal [], JSON.parse(last_response.body)
end
test 'GET /api/statuses/:id returns a status by id' do
status = Status.create!
get "/api/statuses/#{status.id}"
assert_equal status.to_json, last_response.body
end
end
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.
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 ApplicationsAdd API paths to config/application.rb.
# 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.
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:
ActionDispatch::Callbacks.to_prepare do api_reloader.execute_if_updated end
to this:
ActiveSupport::Reloader.to_prepare do api_reloader.execute_if_updated end
See StackOverflow #3282655 for more information.
Active Support InstrumentationGrape has built-in support for ActiveSupport::Notifications which provides simple hook points to instrument key parts of your application.
The following are currently supported:
The main execution of an endpoint, includes filters and rendering.
The execution of the main content block of the endpoint.
The execution of validators.
Serialization or template rendering.
Grape::Formatter::Json)See the ActiveSupport::Notifications documentation for information on how to subscribe to these events.
Grape integrates with following third-party tools:
Grape is work of hundreds of contributors. You're encouraged to submit pull requests, propose features and discuss issues.
See CONTRIBUTING.
See SECURITY for details.
MIT License. See LICENSE for details.
Copyright (c) 2010-2020 Michael Bleigh, Intridea Inc. and Contributors.
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