From: dblack@...
Date: 2003-07-17T23:08:00+09:00
Subject: Re: reliable way of finding Objects Class?

Hello --

On Thu, 17 Jul 2003 walter@mwsewall.com wrote:

> Hi,
>
> is there a reliable way to find the Object's Class.  I know about
> class and type, but what happens if they are overridden?
>
> how do you find it then?
>
> for instance how to find the class at runtime for the following :
>
> class Obj
> 	def class
> 		"Not My Class"
> 	end
>
> 	def type
> 		"don't look here for it"
> 	end
> end

Note that Object#type is on the way out:

  $ ruby -ve '1.type'
  ruby 1.8.0 (2003-06-23) [i686-linux]
  -e:1: warning: Object#type is deprecated; use Object#class

As for finding an object's class without Object#class, I guess you
could do something like:

  >> class Obj; def class; "Go away!"; end; end
  => nil
  >> o = Obj.new
  => #<Obj:0x401e98c8>
  >> a = []; ObjectSpace.each_object(Class) {|c| a << c if o.is_a?(c)}
  => 346
  >> a[-1]
  => Obj

But ObjectSpace.each_object can also be overridden.  There's a finite
number of ways to get this information, none of which as far as I know
is override-proof.


David

-- 
David Alan Black
home: dblack@superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav