Question

I need to create relationships between a user, product and a photo-model. A user can add photos to a product. Therefore, a user has_many photos and a product has_many photos, but each photo belongs_to both a product and a user. How can I achieve this in Rails? As far as I understand a polymorphic association would only allow a photo to belong to a product or a user. Do I have to instead using separate has_many_through relationships for the user-photo and product-photo relationships?

Answer 1

You can have multiple belongs_to attributes within the same model. Essentially the Model that is marked as belongs_to will hold a foreign key to the Model that has been marked with has_many.

class MyModel < ActiveRecord::Base

  belongs_to :other_model1
  belongs_to :other_model2

end

If you want to use polymorphic associates as you mentioned below you could do that along these lines

class Photos < ActiveRecord::Base
  belongs_to :imageable, :polymorphic => true
end

class Users < ActiveRecord::Base
  has_many :photos, :as => :imageable
end

class Product < ActiveRecord::Base
  has_many :photos, :as => :imageable
end

In this case you can create the relationship simply by adding the has_many :phots, :as => :imageable attribute without having to revisit the Photos class.