From: Brian Candler <B.Candler@...>
Date: 2003-07-02T22:50:30+09:00
Subject: Re: anonymous classes

On Wed, Jul 02, 2003 at 05:36:21PM +0900, Dominik Werder wrote:
> > What you've written is called a "singleton class". I wrote this a while:
> >
> > http://www.rubygarden.org/ruby?SingletonTutorial
> 
> 
> it is very helpful for me too :)
> 
> One question referring to
> "A neat solution then is to create a singleton class for each POP3 
> connection as it arrives: "
> How much memory does this technique consume? Are the new methods created 
> for each individual instance? Or just something like a lookup table?

All that happens is that a new proxy class is added to the object, which
points at the module which you #extended it with. It certainly doesn't copy
all the methods.

You can prove this easily enough, by modifying the module *after* you have
done extend:

  module A
  end
  a = "hello"
  a.extend A
  b = "world"
  b.extend A

  module A
    def foo
      puts "it works"
    end
  end
  a.foo     #=> "it works"
  b.foo     #=> "it works"

You can see that the two objects share the same module implementation.

Regards,

Brian.