method_defined_within?

# File activerecord/lib/active_record/attribute_methods.rb, line 109
      def method_defined_within?(name, klass, sup = klass.superclass)
        if klass.method_defined?(name) || klass.private_method_defined?(name)
          if sup.method_defined?(name) || sup.private_method_defined?(name)
            klass.instance_method(name).owner != sup.instance_method(name).owner
          else
            true
          end
        else
          false
        end
      end