Resolve all ActiveRecord Associations using Grape::Entity (SQL Join)

Question

Question

I've been messing with ruby, grape, grape-entity, and activerecord. Everything is going swimmingly however I can't see to get the desired result from grape-entity when using the using keyword for a expose item.

My goal is to basically resolve all my activerecord associations, and then return the resulting JSON. This way I have a complete object for presentation for my configurations API method.

If you need more information, please ask i'll happily provide anything and everything.

Notes: I am using rackup as my server, i'm not using rails at all.

Classes

console_game.rb

class ConsoleGame < ActiveRecord::Base
  self.table_name = 'console_game'
  self.primary_key = :id

  has_many :configurations, :class_name => 'Configuration'

  class Entity < Grape::Entity
    expose :id
    expose :value, :as => :console_game
  end
end

cloud_user.rb

class CloudUser < ActiveRecord::Base
    self.primary_key = :username

    has_many :configurations, :class_name => 'Configuration'
    has_many :favorites, :class_name => 'Favorite', :foreign_key => :username

    class Entity < Grape::Entity
      expose :username, :email, :first_name, :last_name
    end
end

device.rb

class Device < ActiveRecord::Base
    self.table_name = 'device'
    self.primary_key = :id

    has_many :configurations, :class_name => 'Configuration'

    class Entity < Grape::Entity
      expose :id
      expose :name, :as => :device
    end
end

console_system.rb

class ConsoleSystem < ActiveRecord::Base
    self.table_name = 'console_system'
    self.primary_key = :id

    has_many :configurations, :class_name => 'Configuration'

    class Entity < Grape::Entity
      expose :id
      expose :value, :as => :console_system
    end
end

configuration.rb

class Configuration < ActiveRecord::Base
  self.table_name = 'configuration'
  self.primary_key = :id

  belongs_to :console_system, :class_name => 'ConsoleSystem', primary_key: :id, foreign_key: :system_id
  belongs_to :cloud_user, :class_name => 'CloudUser', primary_key: :username, foreign_key: :creator
  belongs_to :device, :class_name => 'Device', primary_key: :id, foreign_key: :device_id
  belongs_to :console_game, :class_name => 'ConsoleGame', primary_key: :id, foreign_key: :console_game_id

  scope :by_system,->(system){
    system_ids = ConsoleSystem.where(value: system).pluck(:id)
    where(system_id: system_ids)
  }

  scope :by_user,->(user){
    user_ids = CloudUser.where(username: user).pluck(:username)
    where(creator: user_ids)
  }

  scope :by_device,->(device){
    device_ids = Device.where(name: device).pluck(:id)
    where(device_id: device_ids)
  }

  scope :by_game,->(game){
    game_ids = ConsoleGame.where(value: game).pluck(:id)
    where(console_game_id: game_ids)
  }

  class Entity < Grape::Entity
    expose :id
    expose :value
    expose :device_id, :as => :device, using: Device::Entity
    expose :system_id, :as => :console_system, using: ConsoleSystem::Entity
    expose :console_game_id, :as => :console_game, using: ConsoleGame::Entity
    expose :creator, :as => :creator, using: CloudUser::Entity
    expose :created_date
    expose :positive_votes
    expose :negative_votes
  end
end

---

Grape API

resource :configuration do
  desc "Returns all configurations."
  get do
    configs = Configuration.includes(:device, :console_system, :cloud_user, :console_game)
    present :data, configs, :with => Configuration::Entity
    present :status, "Success"
  end
end

Error

NoMethodError at /configuration undefined method `id' for 4:Fixnum

Ruby /Library/Ruby/Gems/2.0.0/gems/grape-entity-0.4.2/lib/grape_entity/entity.rb: in delegate_attribute, line 465 Web GET localhost/configuration

Removing :using to get it to "work"

configuration.rb

class Entity < Grape::Entity
    expose :id
    expose :value
    expose :device_id, :as => :device#, using: Device::Entity
    expose :system_id, :as => :console_system#, using: ConsoleSystem::Entity
    expose :console_game_id, :as => :console_game#, using: ConsoleGame::Entity
    expose :creator, :as => :creator#, using: CloudUser::Entity
    expose :created_date
    expose :positive_votes
    expose :negative_votes
end

JSON Result

{
    data: [
        {
            id: 1,
            value: "configuration data 1 example",
            device: 4,
            console_system: 1,
            console_game: 1,
            creator: "manster",
            created_date: null,
            positive_votes: 0,
            negative_votes: 0
        },
        {
            id: 2,
            value: "configuration data 2 example",
            device: 4,
            console_system: null,
            console_game: 2,
            creator: "Zombieguy",
            created_date: null,
            positive_votes: 0,
            negative_votes: 0
        },
        {
            id: 3,
            value: "configuration data 3 example",
            device: 4,
            console_system: null,
            console_game: 3,
            creator: "Justin13692",
            created_date: null,
            positive_votes: 0,
            negative_votes: 0
        }
    ],
    status: "Success"
}

Desired Result

{
    data: [
        {
            id: 1,
            value: "configuration data 1 example",
            device: {
                id: 4,
                device: "XIM Edge"
            },
            console_system: {
                id: 1,
                console_system: "Xbox 360"
            }
            console_game: {
                id: 1,
                console_game: "Gears of War 3"
            },
            creator: {
                username: "manster",
                email: null,
                first_name: null,
                last_name: null
            },
            created_date: null,
            positive_votes: 0,
            negative_votes: 0
        },
        {
            id: 2,
            value: "configuration data 2 example",
            device: {
                id: 4,
                device: "XIM Edge"
            },
            console_system: null,
            console_game: {
                id: 2,
                console_game: "Battlefield 3"
            },
            creator: {
                username: "Zombieguy",
                email: null,
                first_name: null,
                last_name: null
            },
            created_date: null,
            positive_votes: 0,
            negative_votes: 0
        },
        {
            id: 3,
            value: "configuration data 3 example",
            device: {
                id: 4,
                device: "XIM Edge"
            },
            console_system: null,
            console_game: {
                id: 3,
                console_game: "Call of Duty: Modern Warfare 3"
            },
            creator: {
                username: "Justin13692",
                email: null,
                first_name: null,
                last_name: null
            },
            created_date: null,
            positive_votes: 0,
            negative_votes: 0
        }
    ],
    status: "Success"
}

Answer 1

I'm not overly familiar with grape-entity but I think you need to define Configuration::Entity as follows:

class Entity < Grape::Entity
  expose :id
  expose :value
  expose :device, using: Device::Entity
  expose :console_system, using: ConsoleSystem::Entity
  expose :console_game, using: ConsoleGame::Entity
  expose :cloud_user, :as => :creator, using: CloudUser::Entity
  expose :created_date
  expose :positive_votes
  expose :negative_votes
end

What you want to be exposing are the objects associated with a Configuration, not simply their foreign-key IDs.

The error message you're seeing is caused by your code trying to format, say, device_id, which is a number (a Fixnum), as a Device object. Device::Entity specifies exposing the id and name attributes, but as there are no corresponding methods defined on the number 4 the interpreter raises a NoSuchMethod error.