From: Robert Dober <robert.dober@...>
Date: 2006-08-29T08:07:40+09:00
Subject: Re: Partial append_features?

------=_Part_184541_10063997.1156806456734
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

On 8/28/06, Logan Capaldo <logancapaldo@gmail.com> wrote:
>
>
> On Aug 28, 2006, at 3:00 PM, Ola Bini wrote:
>
> > Hi,
> >
> > I'm looking for a way to copy methods from a Module, or specify
> > more directly which methods get included in a class. More or less,
> > I would like to be able to do something like this:
> >
> > module Foo
> >   def do_one_thing
> >   end
> >   def do_second
> >   end
> >   def do_third
> >   end
> > end
> >
> > class Bar
> >   append_from Foo, :do_second, :do_third
> > end
> >
> > or
> > module Baz
> >   append_from Foo, :do_second, :do_third
> > end
> >
> > and I would have a module Baz which could be included, without
> > having do_one_thing included.
> >
> > Is this possible in Ruby right now? My first approach was to get
> > the UnboundMethod instance_method from the Module, but I couldn't
> > find a way to attach these to an unrelated class since
> > UnboundMethod must have a is_a?-relationship with the binding object.
> >
> > Regards
> > --
> >  Ola Bini (http://ola-bini.blogspot.com)
> >  JvYAML, RbYAML, JRuby and Jatha contributor
> >  System Developer, Karolinska Institutet (http://www.ki.se)
> >  OLogix Consulting (http://www.ologix.com)
> >
> >  "Yields falsehood when quined" yields falsehood when quined.
> >
> >
>
> % cat Projects/Ruby Experiments/append_from.rb
> class Module
>    def append_from( mod, *methods_to_keep )
>      methods_to_keep.map! { |m| m.to_s }
>      methods_to_remove =3D mod.instance_methods(false) - methods_to_keep
>      new_mod =3D Module.new
>      new_mod.module_eval do
>        include mod
>        methods_to_remove.each { |meth| undef_method meth }
>      end
>      include new_mod
>    end
> end
>
> module M
>    def a
>      puts "a"
>    end
>
>    def b
>      puts "b"
>    end
> end
>
> class A
>    append_from M, :b
> end
>
> a =3D A.new
> a.b
> a.a
>
> % ruby Projects/Ruby Experiments/append_from.rb
> b
> -:40: undefined method `a' for #<A:0x1e89b4> (NoMethodError)
>
>
>
>
>
unfortunately that approach undefines eralier defined methods in the
appendee, especially inherited ones :(
I guess that could be fixed but the code will become rather clumsy.

Cheers
Robert

--=20
Deux choses sont infinies : l'univers et la b=EAtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

------=_Part_184541_10063997.1156806456734--