From: Stefano Crocco <stefano.crocco@...>
Date: 2008-01-10T19:54:17+09:00
Subject: Re: how to remove a method from an object ?

Alle giovedì 10 gennaio 2008, botp ha scritto:
> On Jan 10, 2008 6:12 PM, Stefano Crocco <stefano.crocco@alice.it> wrote:
> > class << s1
> >   undef_method :print
> > end
>
> ah, undef_,
>
> how does it compare then if i do,
> class << s1
>   remove_method :print
> end
>
> i mean will undef_  do a remove or what?
>
> but anyway, that is cool Stefano. thanks for the new i've just learned.
>
> kind regards -botp

Well, in general remove_method will remove it only from the class where it's 
called. If a superclass defines the same method, the superclass's method will 
be called. According to ri, instead, undef_method, prevents the class from 
responding to the method at all. Here's an example showing the difference

class A
  def test
    puts "test for class A"
  end
end

class B < A
  def test
    puts "test for class B"
  end
end

b = B.new
b.test
=> test for class B

class B
  remove_method :test
end

b.test
=> test for class A

class B
  undef_method :test
end

b.test
=> undefined method `test' for #<B:0xb7c9a754> (NoMethodError)

In my previous post, used undef_method instead of remove_method thinking 
(without trying it) that remove_method would only remove it from the 
singleton class. I tried it now, and I saw it works with both methods. It 
seems singleton classes are treated in a different way.

Stefano