Table of Contents
- What is Grape?
- Stable Release
- Project Resources
- Installation
- Basic Usage
- Mounting
- Versioning
- Describing Methods
- Parameters
- Parameter Validation and Coercion
- Headers
- Routes
- Helpers
- Path Helpers
- Parameter Documentation
- Cookies
- HTTP Status Code
- Redirecting
- Recognizing Path
- Allowed Methods
- Raising Exceptions
- Exception Handling
- Logging
- API Formats
- Content-type
- API Data Formats
- RESTful Model Representations
- Sending Raw or No Data
- Authentication
- Describing and Inspecting an API
- Current Route and Endpoint
- Before and After
- Anchoring
- Using Custom Middleware
- Writing Tests
- Reloading API Changes in Development
- Performance Monitoring
- Contributing to Grape
- License
- Copyright
What is Grape?
Grape is a REST-like API framework for Ruby. It's designed to run on Rack or complement existing web application frameworks such as Rails and Sinatra by providing a simple DSL to easily develop RESTful APIs. It has built-in support for common conventions, including multiple formats, subdomain/prefix restriction, content negotiation, versioning and much more.
Stable Release
You're reading the documentation for the next release of Grape, which should be 0.16.3. Please read UPGRADING when upgrading from a previous version. The current stable release is 0.16.2.
Project Resources
- Grape Website
- Need help? Try Grape Google Group or Gitter
- Follow us on Twitter
Installation
Grape is available as a gem, to install it just install the gem:
gem install grape
If you're using Bundler, add the gem to Gemfile.
gem 'grape'
Run bundle install
.
Basic Usage
Grape APIs are Rack applications that are created by subclassing Grape::API
.
Below is a simple example showing some of the more common features of Grape in
the context of recreating parts of the Twitter API.
module Twitter
class API < Grape::API
version 'v1', using: :header, vendor: 'twitter'
format :json
prefix :api
helpers do
def current_user
@current_user ||= User.authorize!(env)
end
def authenticate!
error!('401 Unauthorized', 401) unless current_user
end
end
resource :statuses do
desc 'Return a public timeline.'
get :public_timeline do
Status.limit(20)
end
desc 'Return a personal timeline.'
get :home_timeline do
authenticate!
current_user.statuses.limit(20)
end
desc 'Return a status.'
params do
requires :id, type: Integer, desc: 'Status id.'
end
route_param :id do
get do
Status.find(params[:id])
end
end
desc 'Create a status.'
params do
requires :status, type: String, desc: 'Your status.'
end
post do
authenticate!
Status.create!({
user: current_user,
text: params[:status]
})
end
desc 'Update a status.'
params do
requires :id, type: String, desc: 'Status ID.'
requires :status, type: String, desc: 'Your status.'
end
put ':id' do
authenticate!
current_user.statuses.find(params[:id]).update({
user: current_user,
text: params[:status]
})
end
desc 'Delete a status.'
params do
requires :id, type: String, desc: 'Status ID.'
end
delete ':id' do
authenticate!
current_user.statuses.find(params[:id]).destroy
end
end
end
end
Mounting
Rack
The above sample creates a Rack application that can be run from a rackup config.ru
file
with rackup
:
run Twitter::API
And would respond to the following routes:
GET /api/statuses/public_timeline
GET /api/statuses/home_timeline
GET /api/statuses/:id
POST /api/statuses
PUT /api/statuses/:id
DELETE /api/statuses/:id
Grape will also automatically respond to HEAD and OPTIONS for all GET, and just OPTIONS for all other routes.
ActiveRecord without Rails
If you want to use ActiveRecord within Grape, you will need to make sure that ActiveRecord's connection pool is handled correctly.
The easiest way to achieve that is by using ActiveRecord's ConnectionManagement
middleware in your
config.ru
before mounting Grape, e.g.:
use ActiveRecord::ConnectionAdapters::ConnectionManagement
run Twitter::API
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 [API, Web]
Rails
Place API files into app/api
. Rails expects a subdirectory that matches the name of the Ruby module and a file name that matches the name of the class. In our example, the file name location and directory for Twitter::API
should be app/api/twitter/api.rb
.
Modify application.rb
:
config.paths.add File.join('app', 'api'), glob: File.join('**', '*.rb')
config.autoload_paths += Dir[Rails.root.join('app', 'api', '*')]
Modify config/routes
:
mount Twitter::API => '/'
Additionally, if the version of your Rails is 4.0+ and the application uses the default model layer of ActiveRecord, you will want to use the hashie-forbidden_attributes gem. This gem disables the security feature of strong_params
at the model layer, allowing you the use of Grape's own params validation instead.
# Gemfile
gem 'hashie-forbidden_attributes'
See below for additional code that enables reloading of API changes in development.
Modules
You can mount multiple API implementations inside another one. These don't have to be different versions, but may be components of the same API.
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
Versioning
There are four strategies in which clients can reach your API's endpoints: :path
,
:header
, :accept_version_header
and :param
. The default strategy is :path
.
Path
version 'v1', using: :path
Using this versioning strategy, clients should pass the desired version in the URL.
curl http://localhost:9292/v1/statuses/public_timeline
Header
version 'v1', using: :header, vendor: 'twitter'
Currently, Grape only supports versioned media types in the following format:
vnd.vendor-and-or-resource-v1234+format
Basically all tokens between the final -
and the +
will be interpreted as the version.
Using this versioning strategy, clients should pass the desired version in the HTTP Accept
head.
curl -H Accept:application/vnd.twitter-v1+json http://localhost:9292/statuses/public_timeline
By default, the first matching version is used when no Accept
header is
supplied. This behavior is similar to routing in Rails. To circumvent this default behavior,
one could use the :strict
option. When this option is set to true
, a 406 Not Acceptable
error
is returned when no correct Accept
header is supplied.
When an invalid Accept
header is supplied, a 406 Not Acceptable
error is returned if the :cascade
option is set to false
. Otherwise a 404 Not Found
error is returned by Rack if no other route
matches.
Accept-Version Header
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.
Param
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
Describing Methods
You can add a description to API methods and namespaces.
desc 'Returns your public timeline.' do
detail 'more details'
params API::Entities::Status.documentation
success API::Entities::Entity
failure [[401, 'Unauthorized', 'Entities::Error']]
named 'My named route'
headers XAuthToken: {
description: 'Valdates your identity',
required: true
},
XOptionalHeader: {
description: 'Not really needed',
required: false
}
end
get :public_timeline do
Status.limit(20)
end
detail
: A more enhanced descriptionparams
: Define parameters directly from anEntity
success
: (former entity) TheEntity
to be used to present by default this routefailure
: (former http_codes) A definition of the used failure HTTP Codes and Entitiesnamed
: A helper to give a route a name and find it with this name in the documentation Hashheaders
: A definition of the used Headers
Parameters
Request parameters are available through the params
hash object. This includes GET
, POST
and PUT
parameters, along with any named parameters you specify in your route strings.
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:
- route string parameters
GET
,POST
andPUT
parameters- the contents of the request body on
POST
andPUT
route string parameters will have precedence.
Declared
Grape allows you to access only the parameters that have been declared by your params
block. It filters out the params that have been passed, but are not allowed. Consider the following API endpoint:
format :json
post 'users/signup' do
{ 'declared_params' => declared(params) }
end
If we do not specify any params, declared
will return an empty Hashie::Mash
instance.
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 params.
format :json
params do
requires :user, type: Hash do
requires :first_name, type: String
requires :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"
}
}
}
The returned hash is a Hashie::Mash
instance, allowing you to access parameters via dot notation:
declared(params).user == declared(params)['user']
The #declared
method is not available to before
filters, as those are evaluated prior
to parameter coercion.
Include missing
By default declared(params)
includes parameters that have nil
values. If you want to return only the parameters that are not nil
, you can use the include_missing
option. By default, include_missing
is set to true
. Consider the following API:
format :json
params do
requires :first_name, type: String
optional :last_name, type: String
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": {
"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"}
}
}
}
Parameter Validation and Coercion
You 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 do
requires :url
end
optional :audio 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
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
Supported Parameter Types
The following are all valid types, supported out of the box by Grape:
- Integer
- Float
- BigDecimal
- Numeric
- Date
- DateTime
- Time
- Boolean
- String
- Symbol
- Rack::Multipart::UploadedFile (alias
File
) - JSON
Custom Types and Coercions
Aside from the default set of supported types listed above, any class can be
used as a type so 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 raise an exception to indicate the value was invalid. E.g.,
class Color
attr_reader :value
def initialize(color)
@value = color
end
def self.parse(value)
fail 'Invalid color' unless %w(blue red green).include?(value)
new(value)
end
end
# ...
params do
requires :color, type: Color, default: Color.new('blue')
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(:decode)
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
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
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
# Parameter will be wrapped using Hashie:
params.avatar.filename # => 'avatar.png'
params.avatar.type # => 'image/png'
params.avatar.tempfile # => #<File>
end
JSON
Types
First-Class 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
.
Multiple Allowed Types
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
Dependent Parameters
Suppose some of your parameters are only relevant if another parameter is given;
Grape allows you to express this relationship through the given
method in your
parameters block, like so:
params do
optional :shelf_id, type: Integer
given :shelf_id do
requires :bin_id, type: Integer
end
end
Built-in Validators
allow_blank
Parameters can be defined as allow_blank
, ensuring that they contain a value. By default, requires
only validates that a parameter was sent in the request, regardless its value. With allow_blank: false
,
empty values or whitespace only values are invalid.
allow_blank
can be combined with both requires
and optional
. If the parameter is required, it has to contain
a value. If it's optional, it's possible to not send it in the request, but if it's being sent, it has to have
some value, and not an empty string/only whitespaces.
params do
requires :username, allow_blank: false
optional :first_name, allow_blank: false
end
values
Parameters can be restricted to a specific set of values with the :values
option.
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.
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 that both range endpoints have to be a #kind_of?
your :type
option (if you don't supplied 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.
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
regexp
Parameters can be restricted to match a specific regular expression with the :regexp
option. If the value
does not match the regular expression an error will be returned. Note that this is true for both requires
and optional
parameters.
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
mutually_exclusive
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.
exactly_one_of
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
at_least_one_of
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
all_or_none_of
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
end
mutually_exclusive
, exactly_one_of
, at_least_one_of
, all_or_none_of
Nested All of these methods can be used at any nested level.
params do
requires :food do
optional :meat
optional :fish
optional :rice
at_least_one_of :meat, :fish, :rice
end
group :drink do
optional :beer
optional :wine
optional :juice
exactly_one_of :beer, :wine, :juice
end
optional :dessert do
optional :cake
optional :icecream
mutually_exclusive :cake, :icecream
end
optional :recipe 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
Custom Validators
class AlphaNumeric < Grape::Validations::Base
def validate_param!(attr_name, params)
unless params[attr_name] =~ /\A[[:alnum:]]+\z/
fail Grape::Exceptions::Validation, params: [@scope.full_name(attr_name)], message: 'must consist of alpha-numeric characters'
end
end
end
params do
requires :text, alpha_numeric: true
end
You can also create custom classes that take parameters.
class Length < Grape::Validations::Base
def validate_param!(attr_name, params)
unless params[attr_name].length <= @option
fail Grape::Exceptions::Validation, params: [@scope.full_name(attr_name)], message: "must be at the most #{@option} characters long"
end
end
end
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::Base
def validate(request)
# return if the param we are checking was not in request
# @attrs is a list containing the attribute we are currently validating
# in our sample case this method once will get called with
# @attrs being [:admin_field] and once with @attrs being [:admin_false_field]
return unless request.params.key? @attrs.first
# check if admin flag is set to true
return unless @option
# check if user is admin or not
# as an example get a token from request and check if it's admin or not
fail Grape::Exceptions::Validation, params: @attrs, message: 'Can not set admin-only field.' unless request.headers['X-Access-Token'] == 'admin'
end
end
And use it in your endpoint definition as:
params do
optional :admin_field, type: String, admin: true
optional :non_admin_field, type: String
optional :admin_false_field, type: String, admin: false
end
Validation Errors
Validation and coercion errors are collected and an exception of type Grape::Exceptions::ValidationErrors
is raised. If the exception goes uncaught it will respond with a status of 400 and an error message. The validation errors are grouped by parameter name and can be accessed via Grape::Exceptions::ValidationErrors#errors
.
The default response from a Grape::Exceptions::ValidationErrors
is a humanly readable string, such as "beer, wine are mutually exclusive", in the following example.
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
I18n
Grape supports I18n for parameter-related error messages, but will fallback to English if translations for the default locale have not been provided. See en.yml for message keys.
Custom Validation messages
Grape 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
all_or_none_of
params do
optional :beer
optional :wine
optional :juice
all_or_none_of :beer, :wine, :juice, message: "all params are required or none is required"
end
mutually_exclusive
params do
optional :beer
optional :wine
optional :juice
mutually_exclusive :beer, :wine, :juice, message: "are mutually exclusive cannot pass both params"
end
exactly_one_of
params do
optional :beer
optional :wine
optional :juice
exactly_one_of :beer, :wine, :juice, message: {exactly_one: "are missing, exactly one parameter is required", mutual_exclusion: "are mutually exclusive, exactly one parameter is required"}
end
at_least_one_of
params do
optional :beer
optional :wine
optional :juice
at_least_one_of :beer, :wine, :juice, message: "are missing, please specify at least one param"
end
Coerce
params do
requires :int, type: {value: Integer, message: "type cast is invalid" }
end
With Lambdas
params do
requires :name, values: { value: -> { (1..10).to_a }, message: 'not in range from 1 to 10' }
end
Pass symbols for i18n translations
You can pass a symbol if you want i18n translations for your custom validation messages.
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'
With Default
You cannot set a custom message option for Default as it requires interpolation %{option1}: %{value1} is incompatible with %{option2}: %{value2}
. You can change the default error message for Default by changing the incompatible_option_values
message key inside en.yml
params do
requires :name, values: { value: -> { (1..10).to_a }, message: 'not in range from 1 to 10' }, default: 5
end
Headers
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
You can set a response header with header
inside an API.
header 'X-Robots-Tag', 'noindex'
When raising error!
, pass additional headers as arguments.
error! 'Unauthorized', 401, 'X-Error-Detail' => 'Invalid token.'
Routes
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
Helpers
You can define helper methods that your endpoints can use with the helpers
macro by either giving a block or a module.
module StatusHelpers
def user_info(user)
"#{user} has statused #{user.statuses} status(s)"
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 a module
helpers StatusHelpers
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
Path Helpers
If you need methods for generating paths inside your endpoints, please see the grape-route-helpers gem.
Parameter Documentation
You can attach additional documentation to params
using a documentation
hash.
params do
optional :first_name, type: String, documentation: { example: 'Jim' }
requires :last_name, type: String, documentation: { example: 'Smith' }
end
Cookies
You can set, get and delete your cookies very simply using cookies
method.
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: '/'
HTTP Status Code
By default Grape returns a 200 status code for GET
-Requests and 201 for POST
-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
Redirecting
You can redirect to a new url temporarily (302) or permanently (301).
redirect '/statuses'
redirect '/statuses', permanent: true
Recognizing Path
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'
Allowed Methods
When you add a GET
route for a resource, a route for the HEAD
method will also be added automatically. You can disable this
behavior with do_not_route_head!
.
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.
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.
curl -X DELETE -v http://localhost:3000/rt_count/
> DELETE /rt_count/ HTTP/1.1
> Host: localhost:3000
>
< HTTP/1.1 405 Method Not Allowed
< Allow: OPTIONS, GET, PUT
Raising Exceptions
You can abort the execution of an API method by raising errors with error!
.
error! 'Access Denied', 401
Anything that responds to #to_s
can be given as a first argument to error!
.
error! :not_found, 404
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 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
Handling 404
For Grape to handle all the 404s for your API, it can be useful to use a catch-all. In its simplest form, it can be like:
route :any, '*path' do
error! # or something else
end
It is very crucial to define this endpoint at the very end of your API, as it literally accepts every request.
Exception Handling
Grape can be told to rescue all exceptions and return them in the API format.
class Twitter::API < Grape::API
rescue_from :all
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
.
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) {
"error: #{message} from #{backtrace}"
}
end
You can also use a module or class.
module CustomFormatter
def self.call(message, backtrace, options, env)
{ 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 specific 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' }).finish
end
end
Or rescue specific exceptions.
class Twitter::API < Grape::API
rescue_from ArgumentError do |e|
error!("ArgumentError: #{e.message}")
end
rescue_from NotImplementedError do |e|
error!("NotImplementedError: #{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
block must return a Rack::Response
object, call error!
or re-raise an exception.
The with
keyword is available as rescue_from
options, it can be passed method name or Proc object.
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
Unrescuable Exceptions
Grape::Exceptions::InvalidVersionHeader
, which is raised when the version in the request header doesn't match the currently evaluated version for the endpoint, will never be rescued from a rescue_from
block (even a rescue_from :all
) This is because Grape relies on Rack to catch that error and try the next versioned-route for cases where there exist identical Grape endpoints with different versions.
Rails 3.x
When mounted inside containers, such as Rails 3.x, errors such as "404 Not Found" or
"406 Not Acceptable" will likely be handled and rendered by Rails handlers. For instance,
accessing a nonexistent route "/api/foo" raises a 404, which inside rails will ultimately
be translated to an ActionController::RoutingError
, which most likely will get rendered
to a HTML error page.
Most APIs will enjoy preventing downstream handlers from handling errors. You may set the
:cascade
option to false
for the entire API or separately on specific version
definitions,
which will remove the X-Cascade: true
header from API responses.
cascade false
version 'v1', using: :header, vendor: 'twitter', cascade: false
Logging
Grape::API
provides a logger
method which by default will return an instance of the Logger
class from Ruby's standard library.
To log messages from within an endpoint, you need to define a helper to make the logger available in the endpoint context.
class API < Grape::API
helpers do
def logger
API.logger
end
end
post '/statuses' do
# ...
logger.info "#{current_user} has statused"
end
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.
API Formats
Your API can declare which content-types to support by using content_type
. If you do not specify any, Grape will support
XML, JSON, BINARY, and TXT content-types. The default format is :txt
; you can change this with default_format
.
Essentially, the two APIs below are equivalent.
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:
- Use the file extension, if specified. If the file is .json, choose the JSON format.
- Use the value of the
format
parameter in the query string, if specified. - Use the format set by the
format
option, if specified. - Attempt to find an acceptable format from the
Accept
header. - Use the default format, if specified by the
default_format
option. - Default to
:txt
.
For example, consider the following API.
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 anAccept: */*
header) does not have an extension or aformat
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 recognizedformat
parameter, so it will respond with XML.GET /hello.xml?format=json
has a recognized extension (which takes precedence over theformat
parameter), so it will respond with XML.GET /hello.xls
(with anAccept: */*
header) has an extension, but that extension is not recognized, so it will respond with JSON (the default format).GET /hello.xls
with anAccept: application/xml
header has an unrecognized extension, but theAccept
header corresponds to a recognized format, so it will respond with XML.GET /hello.xls
with anAccept: text/plain
header has an unrecognized extension and an unrecognizedAccept
header, so it will respond with JSON (the default format).
You can override this process explicitly by specifying env['api.format']
in the API itself.
For example, the following API will let you upload arbitrary files and return their contents as an attachment with the correct MIME type.
class Twitter::API < Grape::API
post 'attachment' do
filename = params[:file][:filename]
content_type MIME::Types.type_for(filename)[0].to_s
env['api.format'] = :binary # there's no formatter for :binary, data will be returned "as is"
header 'Content-Disposition', "attachment; filename*=UTF-8''#{CGI.escape(filename)}"
params[:file][:tempfile].read
end
end
You can have your API only respond to a single format with format
. If you use this, the API will not respond to file
extensions other than specified in format
. For example, consider the following API.
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 anAccept: 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'sto_json
when available, otherwise callMultiJson.dump
:xml
: use object'sto_xml
when available, usually viaMultiXml
, otherwise callto_s
:txt
: use object'sto_txt
when available, otherwiseto_s
:serializable_hash
: use object'sserializable_hash
when available, otherwise fallback to:json
:binary
: data will be returned "as is"
Response statuses that indicate no content as defined by Rack here will bypass serialization and the body entity - though there should be none - will not be modified.
JSONP
Grape supports JSONP via Rack::JSONP, part of the
rack-contrib gem. Add rack-contrib
to your Gemfile
.
require 'rack/contrib'
class API < Grape::API
use Rack::JSONP
format :json
get '/' do
'Hello World'
end
end
CORS
Grape supports CORS via Rack::CORS, part of the
rack-cors gem. Add rack-cors
to your Gemfile
,
then use the middleware in your config.ru file.
require 'rack/cors'
use Rack::Cors do
allow do
origins '*'
resource '*', headers: :any, methods: :get
end
end
run Twitter::API
Content-type
Content-type is set by the formatter. You can override the content-type of the response at runtime
by setting the Content-Type
header.
class API < Grape::API
get '/home_timeline_js' do
content_type 'application/javascript'
"var statuses = ...;"
end
end
API Data Formats
Grape accepts and parses input data sent with the POST and PUT methods as described in the Parameters
section above. It also supports custom data formats. You must declare additional content-types via
content_type
and optionally supply a parser via parser
unless a parser is already available within
Grape to enable a custom format. Such a parser can be a function or a class.
With a parser, parsed data is available "as-is" in env['api.request.body']
.
Without a parser, data is available "as-is" and in env['api.request.input']
.
The following example is a trivial parser that will assign any input with the "text/custom" content-type
to :value
. The parameter will be available via params[:value]
inside the API call.
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']
.
RESTful Model Representations
Grape supports a range of ways to present your data with some help from a generic present
method,
which accepts two arguments: the object to be presented and the options associated with it. The options
hash may include :with
, which defines the entity to expose.
Grape Entities
Add the grape-entity gem to your Gemfile. Please refer to the grape-entity documentation for more details.
The following example exposes statuses.
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
{
id: 10,
name: 'dgz'
}
It has the same result with
get '/users' do
present :id, 10
present :name, :dgz
end
Hypermedia and Roar
You can use Roar to render HAL or Collection+JSON with the help of grape-roar, which defines a custom JSON formatter and enables presenting entities with Grape's present
keyword.
Rabl
You can use Rabl templates with the help of the grape-rabl gem, which defines a custom Grape Rabl formatter.
Active Model Serializers
You can use Active Model Serializers serializers with the help of the grape-active_model_serializers gem, which defines a custom Grape AMS formatter.
Sending Raw or No Data
In general, use the binary format to send raw data.
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.
You can also set the response to a file with file
.
class API < Grape::API
get '/' do
file '/path/to/file'
end
end
If you want a file to be streamed using Rack::Chunked, use stream
.
class API < Grape::API
get '/' do
stream '/path/to/file'
end
end
Authentication
Basic and Digest Auth
Grape has built-in Basic and Digest authentication (the given block
is executed in the context of the current Endpoint
). Authentication
applies to the current namespace and any children, but not parents.
http_basic do |username, password|
# verify user's password here
{ 'test' => 'password1' }[username] == password
end
http_digest({ realm: 'Test Api', opaque: 'app secret' }) do |username|
# lookup the user's password here
{ 'user1' => 'password1' }[username]
end
Register custom middleware for authentication
Grape can use custom Middleware for authentication. How to implement these
Middleware have a look at Rack::Auth::Basic
or similar implementations.
For registering a Middleware you need the following options:
label
- the name for your authenticator to use it laterMiddlewareClass
- the MiddlewareClass to use for authenticationoption_lookup_proc
- A Proc with one Argument to lookup the options at runtime (return value is anArray
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 warden-oauth2 or rack-oauth2 for OAuth2 support.
Describing and Inspecting an API
Grape routes can be reflected at runtime. This can notably be useful for generating documentation.
Grape exposes arrays of API versions and compiled routes. Each route contains a route_prefix
, route_version
, route_namespace
, route_method
, route_path
and route_params
. You can add custom route settings to the route metadata with route_setting
.
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.
Please use Route#xyz
instead.
Note that difference of Route#options
and Route#settings
.
The options
can be referred from your route, it should be set by specifing key and value on verb methods such as get
, post
and put
.
The settings
can also be referred from your route, but it should be set by specifing key and value on route_setting
.
Current Route and Endpoint
It's possible to retrieve the information about the current route from within an API call with route
.
class MyAPI < Grape::API
desc 'Returns a description of a parameter.'
params do
requires :id, type: Integer, desc: 'Identity.'
end
get 'params/:id' do
route.route_params[params[:id]] # yields the parameter description
end
end
The current endpoint responding to the request is self
within the API block
or env['api.endpoint']
elsewhere. The endpoint has some interesting properties,
such as source
which gives you access to the original code block of the API
implementation. This can be particularly useful for building a logger middleware.
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 and After
Blocks can be executed before or after every API call, using before
, after
,
before_validation
and after_validation
.
Before and after callbacks execute in the following order:
before
before_validation
- validations
after_validation
- the API call
after
Steps 4, 5 and 6 only happen if validation succeeds.
Examples
Using a simple before
block to set a header
before do
header 'X-Robots-Tag', 'noindex'
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 behaviour 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 behaviour is then:
GET /123 # 'Fixnum'
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 behaviour 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 behaviour 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
Anchoring
Grape by default anchors all request paths, which means that the request URL
should match from start to end to match, otherwise a 404 Not Found
is
returned. However, this is sometimes not what you want, because it is not always
known upfront what can be expected from the call. This is because Rack-mount by
default anchors requests to match from the start to the end, or not at all.
Rails solves this problem by using a anchor: false
option in your routes.
In Grape this option can be used as well when a method is defined.
For instance when your API needs to get part of an URL, for instance:
class TwitterAPI < Grape::API
namespace :statuses do
get '/(*:status)', anchor: false do
end
end
end
This will match all paths starting with '/statuses/'. There is one caveat though:
the params[:status]
parameter only holds the first part of the request url.
Luckily this can be circumvented by using the described above syntax for path
specification and using the PATH_INFO
Rack environment variable, using
env['PATH_INFO']
. This will hold everything that comes after the '/statuses/'
part.
Using Custom Middleware
Grape Middleware
You can make a custom middleware by using Grape::Middleware::Base
.
It's inherited from some grape official middlewares in fact.
For example, you can write a middleware to log application exception.
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' }, ['Overwrited.']]
end
end
Rails Middleware
Note that when you're using Grape mounted on Rails you don't have to use Rails middleware because it's already included into your middleware stack.
You only have to implement the helpers to access the specific env
variable.
Remote IP
By default you can access remote IP with request.ip
. This is the remote IP address implemented by Rack. Sometimes it is desirable to get the remote IP Rails-style with ActionDispatch::RemoteIp
.
Add gem 'actionpack'
to your Gemfile and require 'action_dispatch/middleware/remote_ip.rb'
. Use the middleware in your API and expose a client_ip
helper. See this documentation for additional options.
class API < Grape::API
use ActionDispatch::RemoteIp
helpers do
def client_ip
env['action_dispatch.remote_ip'].to_s
end
end
get :remote_ip do
{ ip: client_ip }
end
end
Writing Tests
Writing Tests with Rack
Use rack-test
and define your API as app
.
RSpec
You can test a Grape API with RSpec by making HTTP requests and examining the response.
require 'spec_helper'
describe Twitter::API do
include Rack::Test::Methods
def app
Twitter::API
end
context 'GET /api/statuses/public_timeline' do
it 'returns an empty array of statuses' do
get '/api/statuses/public_timeline'
expect(last_response.status).to eq(200)
expect(JSON.parse(last_response.body)).to eq []
end
end
context 'GET /api/statuses/:id' do
it 'returns a status by id' do
status = Status.create!
get "/api/statuses/#{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
Airborne
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
MiniTest
require 'test_helper'
class Twitter::APITest < MiniTest::Test
include Rack::Test::Methods
def app
Twitter::API
end
def test_get_api_statuses_public_timeline_returns_an_empty_array_of_statuses
get '/api/statuses/public_timeline'
assert last_response.ok?
assert_equal [], JSON.parse(last_response.body)
end
def test_get_api_statuses_id_returns_a_status_by_id
status = Status.create!
get "/api/statuses/#{status.id}"
assert_equal status.to_json, last_response.body
end
end
Writing Tests with Rails
RSpec
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
MiniTest
class Twitter::APITest < ActiveSupport::TestCase
include Rack::Test::Methods
def app
Rails.application
end
test 'GET /api/statuses/public_timeline returns an empty array of statuses' do
get '/api/statuses/public_timeline'
assert last_response.ok?
assert_equal [], JSON.parse(last_response.body)
end
test 'GET /api/statuses/:id returns a status by id' do
status = Status.create!
get "/api/statuses/#{status.id}"
assert_equal status.to_json, last_response.body
end
end
Stubbing Helpers
Because helpers are mixed in based on the context when an endpoint is defined, it can
be difficult to stub or mock them for testing. The Grape::Endpoint.before_each
method
can help by allowing you to define behavior on the endpoint that will run before every
request.
describe 'an endpoint that needs helpers stubbed' do
before do
Grape::Endpoint.before_each do |endpoint|
allow(endpoint).to receive(:helper_name).and_return('desired_value')
end
end
after do
Grape::Endpoint.before_each nil
end
it 'stubs the helper' do
# ...
end
end
Reloading API Changes in Development
Reloading in Rack Applications
Use grape-reload.
Reloading in Rails Applications
Add API paths to config/application.rb
.
# 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
See StackOverflow #3282655 for more information.
Performance Monitoring
Active Support Instrumentation
Grape has built-in support for ActiveSupport::Notifications which provides simple hook points to instrument key parts of your application.
The following are currently supported:
endpoint_run.grape
The main execution of an endpoint, includes filters and rendering.
- endpoint - The endpoint instance
endpoint_render.grape
The execution of the main content block of the endpoint.
- endpoint - The endpoint instance
endpoint_run_filters.grape
- endpoint - The endpoint instance
- filters - The filters being executed
- type - The type of filters (before, before_validation, after_validation, after)
See the ActiveSupport::Notifications documentation for information on how to subscribe to these events.
Monitoring Products
Grape integrates with following third-party tools:
- New Relic - built-in support from v3.10.0 of the official newrelic_rpm gem, also newrelic-grape gem
- Librato Metrics - grape-librato gem
- Skylight - skylight gem, documentation
Contributing to Grape
Grape is work of hundreds of contributors. You're encouraged to submit pull requests, propose features and discuss issues.
See CONTRIBUTING.
License
MIT License. See LICENSE for details.
Copyright
Copyright (c) 2010-2015 Michael Bleigh, and Intridea, Inc.