From: "David A. Black" <dblack@...>
Date: 2005-02-11T01:26:55+09:00
Subject: Re: Class of the Instance [was Re: Building a Better Functor]

Hi --

On Thu, 10 Feb 2005, Gavin Kistner wrote:

> Coming from Javascript (where every instance is trivially extensible

Aw, come from Ruby already! :-)

> directly) that seems somewhat cumbersome.

Whoops, I snipped the part you were talking about... but aren't they
in Ruby too?

   o = Object.new
   def o.x; puts "I'm a new method!"; end

> Do many people write things like:
>
> class Object
> 	def instance_class
> 		class<<self; self; end
> 	end
> end
>
> in a common library they re-use frequently? Is there an RCR (or has there 
> been discussion) about adding a simple method like that to the language, so 
> you can simply do:
>
> f = Foo.new
> f.instance_class.class_eval{ ... }

Yes; I submitted such an RCR, for Kernel#singleton_class.  (I know
about the naming issues, but I'd rather not deviate from what Matz
uses at a given time.) See http://www.rcrchive.net/rcr/show/231

> Or (what I'm really looking for) perhaps it might be nice to have a 
> define_method method that worked directly for instances. Hrm, but what would 
> the syntax be? Perhaps that's not such a good idea.

I think that Kernel#singleton_class would work for that purpose, and
would also completely transform people's understanding of the whole
class/singleton-class duality.


David

-- 
David A. Black
dblack@wobblini.net