Cannot destroy existing nested association

Question

I have three models:

class Answer < ActiveRecord::Base
  belongs_to :question
  belongs_to :profile
  belongs_to :theme
  has_many :linked_sources

  attr_accessible :body, :theme_id, :question_id, :linked_sources_attributes
  validates_presence_of :body, :profile, :question, :theme
  has_paper_trail :on => [:update]

  accepts_nested_attributes_for :linked_sources, reject_if: :all_blank
end

class Answer::LinkedSource < ActiveRecord::Base
  belongs_to :answer
  belongs_to :source

  validates :source, :description, presence: true
  validates_presence_of :answer_id, :unless => :nested
  attr_accessor :nested
  accepts_nested_attributes_for :source, reject_if: :all_blank, allow_destroy: true
end

class Source < ActiveRecord::Base
  SOURCE_TYPES = %w(book film)

  has_many :linked_sources, class_name: 'Answer::LinkedSource'
  has_many :answers, through: :linked_sources

  validates :source_type, inclusion: {in: SOURCE_TYPES}
  validates :source_type, :title, presence: true
end

I have a form with two nested already existing Linked Sources + Sources for already existing Answer. In my _linked_source_fields partial I have link_to_remove_association and it works properly, setting the value of "_destroy" input to "1".

When I remove two resources and press submit button, I get the following form data sending out:

utf8:✓
_method:put
authenticity_token:726c1e7NIb0Je2uUZYeKLXmqgFHxgakfcF6fzpjFb38=
answer[theme_id]:2
answer[body]:retert
_wysihtml5_mode:1
answer[question_id]:22
answer[linked_sources_attributes][0][source_id]:3
answer[linked_sources_attributes][0][nested]:
answer[linked_sources_attributes][0][source_attributes][source_type]:book
answer[linked_sources_attributes][0][source_attributes][title]:erger
answer[linked_sources_attributes][0][source_attributes][id]:3
answer[linked_sources_attributes][0][description]:erger ter
answer[linked_sources_attributes][0][_destroy]:1
answer[linked_sources_attributes][0][id]:3
answer[linked_sources_attributes][1][source_id]:4
answer[linked_sources_attributes][1][nested]:
answer[linked_sources_attributes][1][source_attributes][source_type]:film
answer[linked_sources_attributes][1][source_attributes][title]:terter
answer[linked_sources_attributes][1][source_attributes][id]:4
answer[linked_sources_attributes][1][description]:retr
answer[linked_sources_attributes][1][_destroy]:1
answer[linked_sources_attributes][1][id]:4
commit:Готово

And that seems to be correct data.

However after saving this form both linked_sources are still present. The server side just ignores "_destroy" parameters.

What's wrong? I have another cocoon form for another models with simplier nesting (just one level) in this project and it works fine, but in the other case it doesn't.

(As you can notice, my English isn't perfect — sorry about that — it would be fine if you'll correct it)

Answer 1

You must add allow_destroy: true to the association's accepts_nested_attributes_for:

accepts_nested_attributes_for :linked_sources, 
                              reject_if: :all_blank,
                              allow_destroy: true

See the docs for more details.