Remove assosiation instead of destroying object when :allow_destroy => true

Question

When using the new accepts_nested_attributes_for in ActiveRecord, it's possible to use the option :allow_destroy => true. When this option is set, any hash containing nested attributes like {"_delete"=>"1", "id"=>"..."} passed to update_attributes will delete the nested object.

Simple setup:

class Forum < ActiveRecord::Base
  has_many :users
  accepts_nested_attributes_for :users, :allow_destroy => true
end

class User < ActiveRecord::Base
  belongs_to :forum
end

Forum.first.update_attributes("users_attributes"=>{"0"=>{"_delete"=>"1", "id"=>"42"}})

Question: How do I - instead of deleting the nested objects when "_delete" => "1" - just remove the association? (i.e. In the above case set the forum_id on the user to nil)

Bonus question: What if I also want to change the an attribute on the nested object when removing the association? (e.g. like setting a state or a timestamp)

Answer 1

Instead of asking for the user to be deleted using "_delete" => '1', can you not just update it using the nested_attributes?:

Forum.first.update_attributes("users_attributes"=> { 
  "0" => {
    "id" => "42",
    "forum_id" => "",
    "state" => 'removed'
  }
})