AbstractQueryFactoryFactories and alias_method_chain: The Ruby Way(yehudakatz.com)

    class UnboundMethod
      def origin
        owner.instance_method(name)
      end
    end
    
    class Proc
      def to_method(object, method)
        me = self
        object.class.class_eval do
          current = instance_method(method).origin rescue nil
          mine = current.owner == self rescue false
          define_method(method, &me)
          result = instance_method(method)
          mine ? define_method(method, current) : remove_method(method)
          result
        end.bind(object)
      end
    end
    
    class Module
      def redefine(method, &code)
        original = instance_method(method).origin
        define_method(method) do |*args, &block|
          code.to_method(self, method).(original.bind(self), *args, &block)
        end
      end
    end

    Fixnum.redefine(:+) do |old_plus, other|
      if self == 2 and other == 2
        5
      else
        old_plus.(other)
      end
    end

    >> 2 + 2
    => 5
    >> 2 + 3
    => 5
    >> 2 + 1
    => 3