From: Joel VanderWerf <vjoel@...>
Date: 2002-02-19T06:05:44+09:00
Subject: Re: alias danger

Joel VanderWerf wrote:

> Isn't there some way (perhaps in 1.7?) of getting a copy of M's
> implementation of foo as a Proc and redefining foo in terms of a closure
> that refers to this proc? That way, instead of using alias, you'd be
> able to use a local binding that couldn't affect anyone else.

Found it in RiaN: Module#instance_method. This solves half of the
problem:

  module M
    def foo
      p "foo"
    end
  end

  class C; include M; end

  c = C.new

  module M
   Unbound_foo = instance_method :foo
   def foo
     p "foo1"
     Unbound_foo.bind(self).call
   end
  end

  c.foo

    # ==> "foo1"
    #     "foo"

The other half of the problem would be solved if you could use a local
var instead of a constant, and capture it in a closure. Is there
something in 1.7 like this?

  module M
   unbound_foo = instance_method :foo
   define_method :foo {
     p "foo1"
     unbound_foo.bind(self).call
   }
  end

The intent isn't as clear as with alias, but it is certainly safe.

--
Joel VanderWerf                          California PATH, UC Berkeley
mailto:vjoel@path.berkeley.edu                     Ph. (510) 231-9446
http://www.path.berkeley.edu                       FAX (510) 231-9512