define_model_callbacks

define_model_callbacks accepts the same options define_callbacks does, in case you want to overwrite a default. Besides that, it also accepts an :only option, where you can choose if you want all types (before, around or after) or just some.

define_model_callbacks :initializer, :only => :after

Note, the :only => <type> hash will apply to all callbacks defined on that method call. To get around this you can call the define_model_callbacks method as many times as you need.

define_model_callbacks :create, :only => :after
define_model_callbacks :update, :only => :before
define_model_callbacks :destroy, :only => :around

Would create after_create, before_update and around_destroy methods only.

You can pass in a class to before_<type>, after_<type> and around_<type>, in which case the callback will call that class’s <action>_<type> method passing the object that the callback is being called on.

class MyModel
  extend ActiveModel::Callbacks
  define_model_callbacks :create

  before_create AnotherClass
end

class AnotherClass
  def self.before_create( obj )
    # obj is the MyModel instance that the callback is being called on
  end
end