Rails - Issue in has_many through with nested attributes

Question

I am having issue with saving a has_many through relation with nested attributes. Due to complexity and requirment in the application the relation is as follows

Table structure,

agreements:
  id

agreement_rooms:
  id
  agreement_id
  room_id

details:
  id
  agreement_rooms_id

For more clarification, agreement_rooms table is related to many other models which will be having agreement_rooms_id in them.

Rails Associations,

class Agreement < ActiveRecord::Base
  has_many :details,:through => :agreement_rooms
  accepts_nested_attributes_for :details
end

class AgreementRoom < ActiveRecord::Base
  has_many :details
end

class Detail < ActiveRecord::Base
  belongs_to :agreement_room
  accepts_nested_attributes_for :agreement_room
end

When i try to create a agreements record with details hash in it, i get the following error,

Agreement.last.details.create()

ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection: Cannot modify association 'agreement#details' because the source reflection class 'Detail' is associated to 'agreementRoom' via :has_many.

I am not sure how to get this nested attributed working with has_many through relation for the above example. Please help out to figure the issue.

Thanks in advance.

Answer 1

#app/models/aggreement.rb
class Agreement < ActiveRecord::Base
   has_many :agreement_rooms
   accepts_nested_attributes_for :agreement_rooms
end

#app/models/agreement_room.rb
class AgreementRoom < ActiveRecord::Base
   belongs_to :agreement
   belongs_to :room

   has_many :details
   accepts_nested_attributes_for :details
end

#app/models/room.rb
class Room < ActiveRecord::Base
   has_many :agreement_rooms
   has_many :agreements, through: :agreement_rooms
end

#app/models/detail.rb
class Detail < ActiveRecord::Base
   belongs_to :agreement_room
end

--

#app/controllers/agreements_controller.rb
class AgreementsController < ApplicationController
   def new
      @agreement = Agreement.new
      @agreement.agreement_rooms.build.details.build
   end

   def create
      @agreement = Agreement.new agreement_params
      @agreement.save
   end

   private

   def agreement_params
      params.require(:agreement).permit(:agreement, :param, agreement_rooms_attributes: [ details_attributes: [:x] ])
   end
end

#app/views/agreements/new.html.erb
<%= form_for @agreement do |f| %>
   <%= f.fields_for :agreement_rooms do |ar| %>
      <%= ar.fields_for :details do |d| %>
         <%= d.text_field :x %>
      <% end %>
   <% end %>
   <%= f.submit %>
<% end %>