Rails Polymorphic Association with multiple associations on the same model

Question

My question is essentially the same as this one: Polymorphic Association with multiple associations on the same model

However, the proposed/accepted solution does no

Answer 1

None of these solutions seem to work on Rails 5. For some reason, it looks like the behaviour around the association conditions has changed. When assigning the related object, the conditions don't seem to be used in the insert; only when reading the association.

My solution was to override the setter method for the association:

has_one :photo, -> { photo_type: 'primary_photo'},
        as: 'attachable',
        dependent: :destroy

def photo=(photo)
  photo.photo_type = 'primary_photo'
  super
end

Answer 2

None of the previous answers helped me solve this problem, so I'll put this here incase anyone else runs into this. Using Rails 4.2 +.

Create the migration (assuming you have an Addresses table already):

class AddPolymorphicColumnsToAddress < ActiveRecord::Migration
  def change
    add_column :addresses, :addressable_type, :string, index: true
    add_column :addresses, :addressable_id, :integer, index: true
    add_column :addresses, :addressable_scope, :string, index: true
  end
end

Setup your polymorphic association:

class Address < ActiveRecord::Base
  belongs_to :addressable, polymorphic: true
end

Setup the class where the association will be called from:

class Order < ActiveRecord::Base
  has_one :bill_address, -> { where(addressable_scope: :bill_address) }, as: :addressable,  class_name: "Address", dependent: :destroy
  accepts_nested_attributes_for :bill_address, allow_destroy: true

  has_one :ship_address, -> { where(addressable_scope: :ship_address) }, as: :addressable, class_name: "Address", dependent: :destroy
  accepts_nested_attributes_for :ship_address, allow_destroy: true
end

The trick is that you have to call the build method on the Order instance or the scope column won't be populated.

So this does NOT work:

address = {attr1: "value"... etc...}
order = Order.new(bill_address: address)
order.save!

However, this DOES WORK.

address = {attr1: "value"... etc...}
order = Order.new
order.build_bill_address(address)
order.save!

Hope that helps someone else.

Answer 3

Can you add a SecondaryPhoto model like:

class SecondaryPhoto < Photo
end

and then skip the :class_name from the has_one :secondary_photo?

Answer 4

In Rails 5 you have to define attr_accessor for :attachable_id and specify for relation :class_name and :foreign_key options only. You will get ...AND attachable_type = 'SecondaryPhoto' if as: :attachable used

class Post
  attr_accessor :attachable_id
  has_one :photo, :as => :attachable, :dependent => :destroy
  has_one :secondary_photo, -> { where attachable_type: 'SecondaryPhoto' }, class_name: "Photo", dependent: :destroy, foreign_key: :attachable_id

Rails 4.2+

class Photo
   belongs_to :attachable, :polymorphic => true
end

class Post
   has_one :photo, :as => :attachable, :dependent => :destroy
   has_one :secondary_photo, -> { where attachable_type: "SecondaryPhoto"},
     class_name: Photo, foreign_key: :attachable_id,
     foreign_type: :attachable_type, dependent: :destroy
end

You need to provide foreign_key according ....able'ness or Rails will ask for post_id column in photo table. Attachable_type column will fills with Rails magic as SecondaryPhoto