From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2002-12-15T10:58:13+09:00
Subject: Re: un-extending objects

In article <Pine.LNX.4.44.0212141930001.8475-100000@candle.superlink.net>,
 <dblack@candle.superlink.net> wrote:
>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.
>

I like this.  

I've been thinking for a while that it would be nice to be able to 
un-extend an object.  A while back I was doing something where I was 
passing an object around and extending it when it arrived somewhere, but I 
wanted to un-extend it prior to passing it on the next receiver.

Phil

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