instance method define_callbacks

# File activerecord/lib/active_record/observer.rb, line 105
      def define_callbacks(klass)
        observer = self
        observer_name = observer.class.name.underscore.gsub('/', '__')

        ActiveRecord::Callbacks::CALLBACKS.each do |callback|
          next unless respond_to?(callback)
          callback_meth = :"_notify_#{observer_name}_for_#{callback}"
          unless klass.respond_to?(callback_meth)
            klass.send(:define_method, callback_meth) do |&block|
              observer.update(callback, self, &block)
            end
            klass.send(callback, callback_meth)
          end
        end
      end