Question

I would like to destroy a nested model if its attributes are blanked out in the form for the parent model – however, it appears that the ActiveRecord::Callbacks are not called if the model is blank.

class Artist < ActiveRecord::Base
  using_access_control
  attr_accessible :bio, :name, :tour_dates_attributes
  has_many :tour_dates, :dependent => :destroy
  accepts_nested_attributes_for :tour_dates, :reject_if => lambda { |a| a[:when].blank? || a[:where].blank? }, :allow_destroy => true
  validates :bio, :name :presence => true

  def to_param
    name
  end
end

and

class TourDate < ActiveRecord::Base
  validates :address, :when, :where, :artist_id, :presence => true
  attr_accessible :address, :artist_id, :when, :where
  belongs_to :artist
  before_save :destroy_if_blank

  private
  def destroy_if_blank
    logger.info "destroy_if_blank called"
  end
end

I have a form for Artist which uses fields_for to show the fields for the artist’s associated tour dates, which works for editing and adding new tour dates, but if I merely blank out a tour date (to delete it), destroy_if_blank is never called. Presumably the Artist controller’s @artist.update_attributes(params[:artist]) line doesn’t consider a blank entity worth updating.

Am I missing something? Is there a way around this?

Answer 1

You have code that says the record should be ignored if the ‘where’ or the ‘when’ is blank, on the accepts_nested _attributes line, remove the reject_if and your destroy_if blank will likely be called.

Typically to destroy, you would set a _destroy attribute on the nested record, check out the docs http://api.rubyonrails.org/classes/ActiveRecord/NestedAttributes/ClassMethods.html

Also, just used cocoon for some of this today, and thought it was awesome, https://github.com/nathanvda/cocoon