From: Mark Hahn <mchahn@...>
Date: 2001-11-01T04:39:35+09:00
Subject: [ruby-talk:24021] Re: Overiding a method in another module


I think this won't work with instances of subclasses of original C1.

-----Original Message-----
From: wyzzrd@ruby-lang.org [mailto:wyzzrd@ruby-lang.org]On Behalf Of W.
Kent Starr
Sent: Wednesday, October 31, 2001 11:23 AM
To: ruby-talk ML
Subject: [ruby-talk:24018] Re: Overiding a method in another module


Mark Hahn wrote:
>
> I implemented the following.  I think it matches your suggestion.  It
didn't
> work:
>
> module M1
>   class C1
>     def m_1
>       p '1'
>     end
>   end
> end
> include M1
>
> module M2
>     module M1
>       class C1
>         def m_2
>           p '2'
>         end
>       end
>     end
> end
> include M2
>
> C1.new.m_2  -> error: method m_2 undefined
>
> -----Original Message-----
> From: jweirich@one.net [mailto:jweirich@one.net]
> Sent: Wednesday, October 31, 2001 8:26 AM
> To: ruby-talk ML
> Subject: [ruby-talk:23982] Re: Overiding a method in another module
>
> >>>>> "Mark" == Mark Hahn <mchahn@facelink.com> writes:
>
>     Mark> Here is the situation that I am facing (see below).  I want
>     Mark> to add method m_2 to class C1 and make sure instances of C2
>     Mark> (any any other subclass of C1) respond to m_2.  I cannot
>     Mark> subclass C1 to accomplish this because I have no way to
>     Mark> change C2 to subclass my new subclass.  I cannot change the
>     Mark> source of M1 because of the license.  Even if there wasn't a
>     Mark> license issue, isn't reusability all about using other code
>     Mark> without changing it?
>
>     Mark> module M1    << This is other person's module
>     Mark>   class C1
>     Mark>     def m_1
>     Mark>       ...
>     Mark>     end
>     Mark>   end
>     Mark>   class C2 < C1
>     Mark>     ...
>     Mark>   end
>     Mark> end
>
> Just do this in your code somewhere ...
>
>     module M1
>       class C1
>         def m_2
>           ...
>         end
>       end
>     end
>
> Ruby classes are open, so you can add new methods to them without
> touching the original source.
>
> --
> -- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
> ---------------------------------------------------------------------
> "Beware of bugs in the above code; I have only proved it correct,
> not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)

IF i have corrected interpreted your goal (a bi IF), the following
works:

module M1
  class C1
    def m_1
      p '1'
    end
  end
end

# do not touch above ^ or license police will kill you!

module M2
  include M1
  class C1<M1::C1    # extend class C1 from mod M1
    def m_2
      p '2'
    end
  end
end

# did not touch M1 so am safe from license police!

include M2

C1.new.m_1     # ==> 1
C1.new.m_2     # ==> 2

Is this what you want?

Regards,

Kent Starr
elderburn@mindspring.com