:accepts_nested_attributes_for with custom autosave

sample_models.rb

class Address < ActiveRecord::Base
  has_many :phonings, :as => :phonable
  has_many :phone_numbers, :through => :phonings

  accepts_nested_attributes_for :phonings, :allow_destroy => true

end

class Person < ActiveRecord::Base
  has_many :phonings, :as => :phonable
  has_many :phone_numbers, :through => :phonings

end

class Phoning < ActiveRecord::Base
  belongs_to :phone_number, :autosave => true
  belongs_to :phonable, :polymorphic => true

  accepts_nested_attributes_for :phone_number

  def autosave_associated_records_for_phone_number
    if new_phone_number = PhoneNumber.where(:phone_number =>  phone_number.phone_number).first then
      self.phone_number = new_phone_number
    else
      self.phone_number.save!
      self.phone_number_id = self.phone_number.id
    end
  end
end

class PhoneNumber < ActiveRecord::Base
  has_many :phonings, :dependent => :destroy
  has_many :addresses, :through => :phonings, :source => :phonable, :source_type => "Address"
  has_many :people, :through => :phonings, :source => :phonable, :source_type => "Person"
end