Rails: has_many through not returning correctly with namespaced models

Question

I have 3 models. Rom::Favorite, Rom::Card, User. I am having an issue creating the User has_many rom_cards through rom_favorites

Here are my relevant parts of my models

Rom::Card

class Rom::Card < ActiveRecord::Base
    has_many :rom_favorites, class_name: "Rom::Favorite", foreign_key: "rom_card_id", dependent: :destroy

    self.table_name = "rom_cards"

end

User

class User < ActiveRecord::Base
  # Setup accessible (or protected) attributes for your model
  attr_accessible :email, :password, :password_confirmation, :remember_me, :role

  has_many :rom_favorites, class_name: "Rom::Favorite", dependent: :destroy
  has_many :rom_cards, class_name: "Rom::Card", through: :rom_favorites, class_name: "Rom::Favorite"

end

Rom::Favorite

   class Rom::Favorite < ActiveRecord::Base
      attr_accessible :rom_card_id, :user_id

      belongs_to :user
      belongs_to :rom_card, class_name: "Rom::Card"

      validates :user, presence: true
      validates :rom_card, presence: true
      validates :rom_card_id, :uniqueness => {:scope => :user_id}

      self.table_name = "rom_favorites"

    end

All of the utility methods that come along with associations work except

a = User.find(1)
a.rom_cards

The call a.rom_cards returns an empty array and it seems to run this SQL query

SELECT "rom_favorites".* FROM "rom_favorites" INNER JOIN "rom_favorites" "rom_favorites_rom_cards_join" ON "rom_favorites"."id" = "rom_favorites_rom_cards_join"."rom_card_id" WHERE "rom_favorites_rom_cards_join"."user_id" = 1

I am not strong in SQL, but I think this seems correct.

I know a.rom_cards should return 2 cards because a.rom_favorites returns 2 favorites, and in those favorites are card_id's that exist.

The call that should allow rom_cards is the following

has_many :rom_cards, class_name: "Rom::Card", through: :rom_favorites, class_name: "Rom::Favorite"

I feel like the issue has something to do with the fact that it is trying to find the Users cards through favorites and it is looking for card_id (because I specified the class Rom::Card) instead of rom_card_id. But I could be wrong, not exactly sure.

Answer 1

You are duplicating the key class_name in the association hash. There is no need to write class_name: "Rom::Favorite" because by using through: :rom_favorites it will use the configuration options of has_many :rom_favorites.

Try with:

has_many :rom_cards, class_name: "Rom::Card", through: :rom_favorites