From: Rich Kilmer <rich@...>
Date: 2002-12-16T23:03:32+09:00
Subject: Re: un-extending objects

Actually on a somewhat related idea, I wanted to have an object be able
to mixin an eval'ed set of methods.  That way I could dynamically change
them by re-eval'ing changed behavior.  Its for a software agent system I
am playing with...anyway...what I did was have a random module created
for my target "Agent" object which was empty of methods.  I then eval'ed
the method definitions (String) into that module.  Whenever the methods
definitions changed I could then remove all the methods on the module
cleanly and re-eval the defintions.  It works really well, but not at
the granularity your describe below (during a method call).

-rich

> -----Original Message-----
> From: dblack@candle.superlink.net 
> [mailto:dblack@candle.superlink.net] 
> Sent: Saturday, December 14, 2002 7:46 PM
> To: ruby-talk ML
> Subject: un-extending objects
> 
> 
> Hi --
> 
> I've become intrigued by the idea of unextending objects -- 
> that is, removing capabilities from them module-wise.
> 
> A couple of things that have been mentioned here recently 
> that relate at least very indirectly to this are: the idea of 
> a "clean" root class for objects; and the discussion about 
> inheritance (especially from core classes) leaving an object 
> with "extra" methods.  In general, all of these thoughts seem 
> to pertain to the idea of a the granularity of the modular, 
> "plug-in" capabilities of Ruby objects.
> 
> Anyway, I don't have any big idea in mind.  Just playing 
> around with the idea of being able to add and remove modules 
> at run-time.  My current little testbed for this looks like this:
> 
>   # Object#stretch(aModule) -- extend only for duration of block
>   class Object
>     def stretch(mod)
>       c = class << self; self; end
>       before = methods
>       extend(mod)
>       yield
>       (methods - before).each { |m| c.class_eval {undef_method(m)} }
>     end
>   end
> 
>   # Demo
>   module Stuff
>     def talk; puts "hi"; end
>   end
> 
>   a = [1,2,3]
>   a.stretch(Stuff) { a.talk }   # hi
>   p a.respond_to?(:talk)        # false
> 
> This has a kind of aesthetic or maybe narrative appeal to me: 
> the capabilities required of an object for a given purpose 
> exist only at a kind of flashpoint, the exact place and time 
> where they're needed, and then they disappear again.
> 
> I'm interested in whether people have done things like this 
> before, whether it looks like the kind of thing one would 
> ever actually use, etc.
> 
> 
> David
> 
> -- 
> David Alan Black
> home: dblack@candle.superlink.net
> work: blackdav@shu.edu
> Web:  http://pirate.shu.edu/~blackdav
> 
> 
> 
>