From: Trans <transfire@...>
Date: 2008-03-23T04:21:17+09:00
Subject: Re: #meta

Hi Robert,

On Mar 22, 9:39 am, Robert Klemme <shortcut...@googlemail.com> wrote:
> I am feeling stupid because I seem to overlook something: what is the
> advantage of your approach vs.
>
> class Object
>    def meta
>      class<<self;self;end
>    end
> end
>
> ?  As far as I can see your functor in this case simply delegates all
> method invocations to the singleton class.  Why not directly use /
> return it?

Try it:

>> class X
>>   meta.attr_accessor
>> end
NoMethodError: private method `attr_accessor' called for #<Class:X>
        from (irb):7

> While I think about it you could even do:
>
> class Object
>    def meta(&b)
>      cl = class<<self;self;end
>      cl.class_eval(&b) if b
>      cl
>    end
> end
>
> class Some
>    meta do
>      attr_accessor :foo
>
>      def incr
>        self.foo += 1
>      end
>    end
> end

There's no need for meta at all, you could just use "class << self"
directly,

  class Some
    class << self
      attr_accessor :foo

      def incr
        self.foo += 1
      end
    end
  end

But just as some people prefer to use "def self.foo", it's nice to use
module level methods like #class_attr_accessor.  That's were #meta
comes in as generalized form rather than defining class level
equivalents for all possible methods.

T.