From: Axel Etzold <AEtzold@...>
Date: 2007-12-25T18:27:44+09:00
Subject: Re: C++ Functors and Ruby extensions


-------- Original-Nachricht --------
> Datum: Tue, 25 Dec 2007 04:02:38 +0900
> Von: "Jason Roelofs" <jameskilton@gmail.com>
> An: ruby-talk@ruby-lang.org
> Betreff: C++ Functors and Ruby extensions

> I wonder if anyone has tried to do what I'm doing and if they've come up
> with an appropriate solution.
> 
> Basic idea:
> 
> struct ruby_func_wrapper
> {
>    VALUE operator()(VALUE self, VALUE args)
>    {
>        m_callback(args ...);
>    }
> }
> 
> extern "C"
> void Init_functor_test() {
>    ruby_func_wrapper functor;
>    [ ... code that sets callback of functor ... ]
> 
>    rb_define_global_function("functor_test", [something here &functor],
> -2);
> }
> 
> Basically, I want to use instances of the ruby_func_wrapper functor as
> callback for Ruby methods. I'm using Boost right now, and have tried
> Boost.Function and Boost.Bind to no avail (the code compiles but the
> actual
> call causes a seg fault, I assume the memory location is voided after the
> init is done, so trying to pass execution to a bad memory location, but
> I'm
> not sure). For the record, I am trying my hand at a Boost.Ruby library.
> 
> I'm also wondering if there is another way to add methods to Kernel or
> Classes outside of the rb_define_* methods. In Python you can do
> PyObject_SetAttr(namespace, name, PyCFunction) which is effectively ("
> namespace.name = function"). I've yet to find an equivalent in Ruby.
> 
> I hope this is clear, though if not I can post the full code I've got
> right
> now.
> 
> Thanks
> 
> Jason

Dear Jason,

I think SWIG (http://www.swig.org/) may have a solution
for what you want to do:

http://www.goto.info.waseda.ac.jp/~fukusima/ruby/swig-examples/funcptr/index.html

Here's some more information on how to use it in conjunction with
Ruby :

http://www.swig.org/Doc1.3/Ruby.html 

Best regards,

Axel 

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