From: Gavin Sinclair <gsinclair@...>
Date: 2004-09-14T08:18:59+09:00
Subject: Re: traits & roles

Phil wrote:
> So you might have:
>
>   class Baz
>   end
>
>   baz = Baz.new
>   baz.extend Foo  #baz now has Foo 'traits'
>
> ....and later you might want to do:
>   baz.unextend Foo #remove the Foo 'traits' from baz
>
> ....later on you could add another set of traits to baz:
>   baz.extend OtherTraits
>
> Of course there is no 'unextend', but there are probably ways to
> implement this.  For example, you could get a list of all of the methods
>  of Foo and undef them in the baz object (couldn't you?)

I'd expect a proper implementation of 'unextend' to just "peel away a
layer of methods", not actually remove them.  So...

  module Foo1
    def foo; "foo1"; end
  end

  module Foo2
    def foo; "foo2"; end
  end

  class X
  end

  x = X.new

  x.foo                   # error

  x.extend Foo1
  x.foo                   # "foo1"

  x.extend Foo2
  x.foo                   # "foo2"

  x.unextend Foo2
  x.foo                   # "foo1"

Gavin