From: Peter Cooper <peter@...>
Date: 2007-06-12T20:18:20+09:00
Subject: Re: self in method name

On 6/12/07, Bertram Scharpf <lists@bertram-scharpf.de> wrote:
> > class Foo
> >     def self.bar
> >         ...
> >     end
> > end
>
> Is this the same thing as
>
>   class Foo
>     class <<self
>       def bar
>           ...
>       end
>     end
>   end

Yes, except in the second you're actually opening up the virtual class
to work on it directly whereas in the first example you're defining
the method using an absolute name.

It's easy to see this as a pattern though without understanding the
background, which, hopefully, a brief example will rectify:

 class << Fixnum
   def x; "y"; end
 end

 puts Fixnum.x  # => "y"
 puts 10.x      # ERROR

Note that you can dig into virtual classes at any time, not just
within the capacity of a class you're currently defining :)

So.. when you see class << self within the definition of another
class, then it's the equivalent of  class << ClassName, and merely
using the "self" to provide the current class rather than naming it
explicitly.

Cheers,
Peter Cooper
http://www.rubyinside.com/