From: "David A. Black" <dblack@...>
Date: 2005-07-12T12:20:21+09:00
Subject: Re: class_attr_accessor

Hi --

On Tue, 12 Jul 2005, Luke Kanies wrote:

> Yeah, that's what I'll be using, since it should work just fine for my
> purposes, but I think it's a touch obfuscated.  Of course, I've already
> admitted to not fully grokking the 'class << self' syntax, so that
> doesn't help.

It puts you in the scope of an object's singleton class (i.e., the
class where those methods reside which are unique to this object).  I
sometimes wonder whether all the "class << self" examples obscure the
fact that this is a general-purpose thing.  In case that's the case,
here's an example:

    str = "I am a string"
    class << str
      def x
        puts "method illustrating singleton class"
      end
    end

at which point you can do:

    str.x

In general, "<< obj" is just a way of telling the "class" keyword that
the class you wish to enter has no name, but is the (anonymous)
singleton class of obj.  You could in fact do:

   class C
     # stuff
   end

and then later:

   class << C
     attr_reader :whatever
   end

which is another non-"self" example.


David

-- 
David A. Black
dblack@wobblini.net