Grape::ActiveModelSerializers

Use active_model_serializers with Grape!

Breaking Changes

v1.0.0

• BREAKING Changes behaviour of root keys when serialising arrays. See Array roots

Installation

Add the grape and grape-active_model_serializers gems to Gemfile.

gem 'grape'
gem 'grape-active_model_serializers'

And then execute:

bundle

Usage

Require grape-active_model_serializers

# config.ru
require 'grape-active_model_serializers'

Tell your API to use Grape::Formatter::ActiveModelSerializers

class API < Grape::API
  format :json
  formatter :json, Grape::Formatter::ActiveModelSerializers
end

Writing serializers

See active_model_serializers

Serializers are inferred by active_record model names

grape-active_model_serializers will search for serializers for the objects returned by your grape API.

namespace :users do
  get ":id" do
    @user = User.find(params[:id])
  end
end

In this case, as User objects are being returned, grape-active_model_serializers will look for a serializer named UserSerializer.

Array roots

When serializing an array, the array root is set to the innermost namespace name if there is one, otherwise it is set to the route name (e.g. get 'name').

namespace :users do
  get ":id" do
    @user = User.find(params[:id])
  end
end
# root = users

get "people" do
  @user = User.all
end
# root = people

Manually specifying serializer options

# Serializer options can be specified on routes or namespaces.
namespace 'foo', :serializer => :bar do
  get "/" do
    # will use "bar" serializer
  end

  # Options specified on a route or namespace override those of the containing namespace.
  get "/home", :serializer => :home do
    # will use "home" serializer
  end

  # All standard options for `ActiveModel::Serializers` are supported.
  get "/fancy_homes", :root => 'world', :each_serializer => :fancy_homes
  ...
  end
end

Custom metadata along with the resources

# Control any additional metadata using meta and meta_key
get "/homes"
  collection = Home.all
  render collection, { meta: { page: 5, current_page: 3 }, meta_key: :pagination_info }
end

current_user

One of the nice features of ActiveModel::Serializers is that it provides access to the authorization context via the current_user.

In Grape, you can get the same behavior by defining a current_user helper method:

  helpers do
    def current_user
      @current_user ||= User.where( :access_token => params[:token]).first
    end

    def authenticate!
      error!('401 Unauthenticated', 401) unless current_user
    end
  end

Then, in your serializer, you could show or hide some elements based on the current user's permissions:

class PostSerializer < ActiveModel::Serializer
...
  def include_admin_comments?
    current_user.roles.member? :admin
  end
end

Full Example

class User < ActiveRecord::Base
  attr_accessor :first_name, :last_name, :password, :email
end

class UserSerializer < ActiveModel::Serializer
  attributes :first_name, :last_name
end

class API < Grape::API
  get("/home") do
    User.new({first_name: 'JR', last_name: 'HE', email: 'contact@jrhe.co.uk'})
  end
end

API.new.get "/home" # => '{:user=>{:first_name=>"JR", :last_name=>"HE"}}'

RSpec

See "Writing Tests" in https://github.com/intridea/grape.

Enjoy :)

Changelog

v1.0.0

• Released on rubygems.org
• BREAKING Changes behaviour of root keys when serialising arrays. See Array roots

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Thanks to

The developers and maintainers of: active_model_serializers Grape!

Structured and based upon grape-rabl.