From: Jim Cain <list@...>
Date: 2003-07-15T15:01:10+09:00
Subject: Re: Custom method_missing doesn't trap super call

Yukihiro Matsumoto wrote:

> In message "Re: Custom method_missing doesn't trap super call"
>     on 03/07/15, Richard Dale <Richard_Dale@tipitina.demon.co.uk> writes:
> 
> |Perhaps I should explain more what about I was trying to do - I didn't want
> |to over complicate the problem description. I'm working on bindings to a
> |C++ gui library Qt, and use a C method_missing (in the C 'Qt' extension) to
> |forward the calls to the C++ methods from ruby. When virtual methods are
> |overriden in ruby, like QPushButton::paintEvent(), it uses rb_respond_to()
> |to see whether or not there is a ruby version of the method.
> 
> I understand what you want.  But why use method_missing?  If Qt has
> finite set of methods, why don't you define wrapper methods just as
> Swig does?
> 
> This does not mean I'm refusing "method_missing for super".  I'm still
> thinking.
> 
> 							matz.
> 
> 

I just had occasion to invent a solution for this in something I was 
working on. Unfortunately, I wasn't paying enough attention to this 
thread beforehand, so I don't know if someone has already recommended a 
solution similar to mine--or even worse, recommended against it. :)

My goal is to wrap the instance variable @obj so that, from the outside
of the Wrapper object, it responds exactly like the @obj would.

---------8<---------
class Wrapper

    # don't respond to any inherited public methods
    (methods - ['__id__', '__send__']).each do |meth|
       begin
          undef_method meth.intern
       rescue
          # ignore
       end
    end

    def initialize(conn, klass, id)
       @obj = ...
    end

    def method_missing(meth, *args)
       @obj.__send__(meth, *args)
    end
---------8<---------

Comments?