Occasionally, you need to do something to a model without invoking callbacks. This is especially necessary for instances where you need to modify the record you just saved in an after_save callback. For example, say you want to create a hash based on the record’s ID. You won’t have the ID until after it’s been saved, and if you call self.save in an after_save callback, you’re going to end up in an endless loop.

It turns out that ActiveRecord has two private methods.

create_without_callbacks

and

update_without_callbacks

Remember that private in Ruby is less about keeping you from calling the methods and more about letting you know that you shouldn’t depend on them. With Ruby’s send method, using either of these in your application is easy.

Note that in Ruby 1.9, send doesn’t allow calling private methods, but send! does.

  class Project < ActiveRecord::Base
    after_save :create_hash_from_name_and_id

    private
      def create_hash_from_name_and_id
        self.hash = Digest::SHA1.hexdigest("#{self.id}#{Time.now.to_s}#{self.name}")
        self.send :update_without_callbacks
      end
  end

It's my opinion that these methods should not be private. If I can skip validations with save(false), then I should be able to skip callbacks as well.

There are other patterns you can use to skip callbacks.

  class Project < ActiveRecord::Base
    attr_accessor :skip_callbacks

    with_options :unless => :skip_callbacks do |project|
      project.after_save :create_hash_from_name_and_id
      project.after_save :do_more_stuff
    end

    private
      def create_hash_from_name_and_id
        self.skip_callbacks = true
        self.hash = Digest::SHA1.hexdigest("#{self.id}#{Time.now.to_s}#{self.name}")
        self.save
      end
  end

So there you go. Go forth and skip callbacks at will.