Parsing JSONAPI using representable gem in Ruby on Rails 4

song_representer_spec.rb

require 'rails_helper'
require 'representable/json'
require 'representable/json/collection'

class Song < OpenStruct
end

# Ex. 1 using standalone collections
class SongRepresenter < Representable::Decorator
  include Representable::JSON
  include Representable::JSON::Collection

    items class: Song do
      property :id
      nested :attributes do
        property :title
      end
    end
end

# Ex. 2 create a module for decorate one element of the object
module SongRepresenter2
  include Representable::JSON

  property :id
  property :type
  nested :attributes do
    property :title
  end
end

class AlbumRepresenter < Representable::Decorator
  include Representable::JSON

  collection :data, decorator: SongRepresenter2, class: Song

end

# Ex. 3 another approach using collection
class SimpleSongRepresenter < Representable::Decorator
  include Representable::JSON
  
  collection :data, class: Song do
    property :id
    property :type
    nested :attributes do
      property :title
    end
  end

end

RSpec.describe "SongRepresenter" do

  it "ex.1 it works for simple_json" do
    songs = SongRepresenter.new([]).from_json(simple_json)
    expect(songs.first.title).to eq("Linoleum")
  end

  it "ex.2 album representer for jsonapi_sample" do
    songs = AlbumRepresenter.new(OpenStruct.new).from_json(jsonapi_sample)
    expect(songs.data.first.class).to eq(Song)
    expect(songs.data.first.id).to eq(1)
    expect(songs.data.first.title).to eq("Linoleum")
  end

  it "ex.3 simple song representer for jsonapi_sample" do
    songs = SimpleSongRepresenter.new(OpenStruct.new).from_json(jsonapi_sample)
    expect(songs.data.first.class).to eq(Song)
    expect(songs.data.first.id).to eq(1)
    expect(songs.data.first.title).to eq("Linoleum")  
  end

  def simple_json
    [{
      id: 1,
      attributes: {
        title: "Linoleum"
      }
        }].to_json
  end

  def jsonapi_sample
    {
      data: [
        id: 1,
        attributes: {
          title: "Linoleum"
        }
      ]
    }.to_json
  end
end