ruby-on-rails - 如何通过多态模型添加 has_many :through？

Question

给定模型：

class User
  has_many :cars
  has_many :foods
end

class Car
  belongs_to :user
  has_many :colors, :as => :owner
end

class Food
  belongs_to :user
  has_many :colors, :as => :owner
end

class Color
  belongs_to :owner, :polymorphic => true   # This can be Food or Car
end

我怎么能说在 Rails 3和Rails 3 上都有User很多？那么 Rails 2 呢？ColorCarFood

Answer 1

我相信这应该为你做（它应该在 Rails 2 和 Rails 3 中都可以工作）：

class User
  has_many :colors
  has_many :cars, :through => :colors, :source => :owner, :source_type => "Car"
  has_many :foods, :through => :colors, :source => :owner, :source_type => "Food"
end

class Color
  belongs_to :user
  belongs_to :owner, :polymorphic => true
end

class Car
  belongs_to :user
  has_many :colors, :as => :owner
end

class Food
  belongs_to :user
  has_many :colors, :as => :owner
end