Question

I was playing around with implementing Rails model callbacks (after_save, before_save) etc. using alias method. All it does is it aliases the save method to save_with_callbacks. It works, except before_save has to be called after save is defined or alias keyword throws an error. I’m still in the process of understanding how Rails callbacks really works, but was wondering if there’s a way to use before_filter anywhere in the model.

module ClassMethods
  def before_save
    class_eval do
      # old_save points to save
      # save points to save_with_callbacks
      alias :old_save :save
      alias :save :save_with_callbacks
    end
  end
end

module InstanceMethods
  def save_with_callbacks
    @save_with_callbacks_text = 'Saving with callbacks'
    old_save
  end
end

class Task
  extend ClassMethods
  include InstanceMethods

  attr_reader :save_text, :save_with_callbacks_text

  def save
    @save_text = 'Saving'
  end

  # Needs to be called after save, save_with_callbacks are defined
  before_save
end

Answer 1

I forgot users don’t generally define ‘save’ method, but let ORM do it for you. Moved save method to InstanceMethods and that solves the problem.