[SOLVED] Using a has_many association with a single table inheritance model in rails

Using a has_many association with a single table inheritance model in rails

I'm trying to create a simple has_many association between my Game and DLC models. The challenge I'm facing is that since there's no DLC table because of the single table inheritance, there's no way to insert a game_id. So if I were to do the following I'd get this error:

game = Game.create
game.dlcs

SQLite3::SQLException: no such column: games.game_id

Here is how my models are currently setup:

class Game < ActiveRecord::Base
    has_many :dlcs
end

class DLC < Game
    belongs_to :game
end

Note: DLC refers to downloadable content

Solution

The simplest alternative would be to just use self-joins and add a parent_id column to games.

class Game < ActiveRecord::Base
  has_many :dlcs unless self.name == 'DLC'
end

class DLC < Game
  belongs_to :game, foreign_key: :parent_id
end

If that's absolutely unthinkable you can create a join table.

# game_id: int
# dlc_id: int
class GameExtension
  belongs_to :game
  belongs_to :dlc
end

class Game < ActiveRecord::Base
  has_many :game_extensions
  has_many :dlcs, though: :game_extensions
end

class DLC < Game
  has_many :game_extensions
  belongs_to :game, though: :game_extensions
end