Comments on: Skipping ActiveRecord Callback Methods

By: Georg Ledermann

Georg Ledermann — Wed, 30 Nov -0001 00:00:00 +0000

Thank you for this tip! But: Your skip_callback method does not handle the result of the yielded block. If have fixed it with this code:

  def self.skip_callback(callback, &block)
    method = instance_method(callback)
    remove_method(callback) if respond_to?(callback)
    define_method(callback){ true }
    result = yield
    remove_method(callback)
    define_method(callback, method)
    result
  end

By: Forexman

Forexman — Wed, 30 Nov -0001 00:00:00 +0000

Hi. This is really interesting post. Thank You! I have just subscribed to Your rss!

Best regards

By: Bart

Bart — Wed, 30 Nov -0001 00:00:00 +0000

Really usefull solution to me! I used this in a module and didn’t get it working on first until I read about the difference between including and extending a module. For all developers getting the same problem, I found a lot of usefull info on this url:

http://www.juixe.com/techknow/index.php/2006/06/15/mixins-in-ruby/

By: Georg Ledermann

Georg Ledermann — Wed, 30 Nov -0001 00:00:00 +0000

One more addition: Bad things happen if an exception is raised in the yielded block – the former callback is not restored. To avoid this I have changed the method like this:

  def self.skip_callback(callback, &block)
    method = instance_method(callback)
    remove_method(callback) if respond_to?(callback)
    define_method(callback){ true }
    begin
      result = yield
    ensure
      # Always redefine the old callback, even if
      # there were exceptions raised in the yielded block
      remove_method(callback)
      define_method(callback, method)
    end
    result
  end

By: Vojtech Salbaba

Vojtech Salbaba — Wed, 30 Nov -0001 00:00:00 +0000

What i find even more interesting is that it works even it the callback itself.

class Person < ActiveRecord::Base
 after_save :create_another

 def create_another
  Person.skip_callback("create_brother") do
   Person.create(:name => "peter")
  end
 end
end

Person.create :name => "ronald"
This code will not explode, even though the method removes itself and then add itself back (gives me headache).

By: Vojtech Salbaba

Vojtech Salbaba — Wed, 30 Nov -0001 00:00:00 +0000

Hm. Please close the pre tag behind me, thank you :)