From: Johann Hibschman <johann@...>
Date: 2001-11-30T04:15:08+09:00
Subject: [ruby-talk:26946] Re: Interfacing to a C++ library (was: overload possible?)

>>>>> "KS" == Kevin Smith <kevinbsmith@yahoo.com> writes:

    KS> For example, you might have a C++ Widget, and Button which
    KS> inherits from Widget. Now on the Ruby side, you want a Ruby
    KS> Widget that inherits from the C++ Widget, and you want a Ruby
    KS> Button that inherits from the C++ Button, BUT ALSO inherits
    KS> from the Ruby Button.

Hm.  I just did this, or think I did.  What was the problem?

My C++ class structure for a Poisson solver was

Problem
  - Problem2
  - Problem3

I created the class objects in Ruby normally...

    cProblem   = rb_define_class_under(mFish, "Problem", rb_cObject);
    cProblem2  = rb_define_class_under(mFish, "Problem2", cProblem);
    cProblem3  = rb_define_class_under(mFish, "Problem3", cProblem);

Defined all the methods of the Problem class under cProblem

    rb_define_singleton_method(cProblem, "new", RB_METHOD(problem_new), 0);
    rb_define_method(cProblem, "smooth", RB_METHOD(problem_smooth), 2);
    rb_define_method(cProblem, "residual", RB_METHOD(problem_residual), 2);

Then just defined the creation methods on cProblem2 and 3:

    rb_define_singleton_method(cProblem2, "new", RB_METHOD(problem2_new), 2); 
    rb_define_singleton_method(cProblem3, "new", RB_METHOD(problem3_new), 2); 

So, what's wrong with this?  Since C++ can cast the pointers to
Problem2 objects to Problem objects, it had no problem with the
wrapper functions.

--Johann