From: s@... (Stefan Schmiedl)
Date: 2002-04-10T10:32:39+09:00
Subject: Re: class << self   question

On Wed, 10 Apr 2002 00:20:05 +0200,
Markus Jais <info@mjais.de> wrote:
> hello
> 
> in several libraries I found this:
> class << self
> 
> now I played with it and generated the following sample
> code (does not do anything useful, just for playing with the concept)
> 
> class Vector
>    def initialize (x, y)
>           @x = x
>           @y = y
>    end
> 

  here self refers to class Vector

>    class << self
>           def func
>                  puts "in func"
>           end
>    end
> 
>    def my_method

  when my_method is evaluated self refers to an instance of class Vector

>           self.func()  # Error!! why does this not work ???
>    end
> 
> end
> 

> I understand that
> class << self 
> in this case generates a class method called "func"

with class << self you are introducing an anonymous super class
whose methods are available for lookup

> 
> but I also thought that 
> class << object
> extends an object 
> (like in the pickaxe book on page 243)

by exactly the same mechanism as above.

> 
> why does this not work with
> class << self ??
> why can I not call
> self.func() in the method "my_method" above ??

because during the definition self is Vector and
during execution self is an instance of Vector.

> 
> maybe I am just doing something wrong.

- meditate over the pictures in the pickaxe book, esp. p. 246
- sprinkle your source with "p self" in strategically important
  places

sorry for not being more clear here, but the last time I tried
to explain this stuff, a reviewer recommended to leave it out
(hi clemens ;->).

s.
--
Stefan Schmiedl
Approximity GmbH                                      http://www.approximity.com
Research & Development                             mailto:stefan@approximity.com
Loreleystr. 5, 94315 Straubing, Germany
Tel. (0 94 21) 74 01 06, Fax (0 94 21) 74 01 21

shhhh ... I can't hear my code!