[C++-sig] wrapping abstract classes question

[David Abrahams]

Roman Yakovenko <roman.yakovenko at gmail.com> writes:

> The are 2 approaches to create wrapper for derived class
> 1.
>
> struct derived_wrapper
>    : derived, boost::python::wrapper< derived >{
>
>  virtual int do_smth(  ){
>         boost::python::override do_smth = this->get_override( "do_smth" );
>         return do_smth(  );
>  }
>
>  virtual int do_smth_else(  ){
>         boost::python::override do_smth_else = this->get_override(
> "do_smth_else" );
>         return do_smth_else(  );
>     }
>
> }
>
> 2.
>
> struct derived_wrapper : derived, base_wrapper,
> boost::python::wrapper< derived >{
>
> virtual int do_smth_else(  ){
>         boost::python::override do_smth_else = this->get_override(
> "do_smth_else" );
>         return do_smth_else(  );
>     }
>
> }
>
> It seems to me that both approaches will work, but I do not know which
> one is better
> ( right ) and which one is not.

This one is tricky.  I think this is probably the best you can do.

        template <class B>
        struct wrap_base : B
        {
            int do_smth()
            {
                return this->get_override("do_smth")();
            };
        };

        struct base_wrapper
           : wrap_base<base>, boost::python::wrapper<base>
        {
        };

        struct derived_wrapper
           : wrap_base<derived>, boost::python::wrapper<derived>
        {
            int do_smth_else()
            {
                return this->get_override("do_smth_else")();
            };
        };

HTH,

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com