From: "David A. Black" <dblack@...>
Date: 2005-03-09T23:06:56+09:00
Subject: Re: Module#dup and Module.remove_method question

Hi --

On Wed, 9 Mar 2005, Renald Buter wrote:

> Hello,
>
> I have a question about Module#dup and Module.remove_method.
>
> Say I have the following:
>
> > module A
> >  def self.foo; puts "A::foo; end
> > end
>
> > B = A.dup
> > B.foo
> "A::foo"
> => nil
>
> But now I want to remove foo from A's duplicate:
>
> > class <<B; remove_method :foo; end
>   NameError: method `foo' not defined in Module
>         from (irb):37:in `remove_method'
>         from (irb):37
>
> Ah? Well OK, let's remove it from A then.
>
> > class <<A; remove_method :foo; end
> => #<Class:A>
>
> Let's test it:
>
> > A.foo
> NoMethodError: undefined method `foo' for A:Module
>        from (irb):40
>        irb(main):041:0>
>
> That works. BUT:
>
> > B.foo
> "A::foo"
> => nil
>
> This, I do not understand: where does B.foo live, now and why can't I
> remove it?

B.foo lives in A (the methods don't get dup'd when the class object is
dup'd), and to remove it from B you can use undef_method.
remove_method will only operate on the module where the method was
defined, whereas undef_method will take it out of the search path of
any module that could see it before.


David

-- 
David A. Black
dblack@wobblini.net