Hi Rento, Got it working now. I did not realize that the wrapper<> automatically handled downcast conversion as well.
Thanks, Paul "Renato Araujo" <rena...@gmail.com> wrote in message news:95291a80907070708p66393027nde354f5b7cc3a...@mail.gmail.com... Hi Paul, You can extend from boost::python::wrapper<T> and use this function to get PyObject from c++ object. namespace detail { .. namespace wrapper_base_ // ADL disabler { inline PyObject* get_owner(wrapper_base const volatile& w); .... BR On Tue, Jul 7, 2009 at 7:54 AM, Paul Scruby<p...@gingernut.tv> wrote: > Hiya, > > I'm trying to pass a C++ class that I've extended in Python to a C++ > function. I found an example of how to do this in David Abrahams article > on > Building Hybrid Systems with Boost Python. > http://www.boostpro.com/writing/bpl.html#virtual-functions > > However, I've not managed to get this example to compile: > > #include <string> > #include <boost/python.hpp> > using namespace boost::python; > > class Base > { > public: > virtual int f(std::string x) { return 42; } > virtual ~Base() {} > }; > > int calls_f(Base & b, std::string x) { return b.f(x); } > > struct BaseWrap : Base > { > BaseWrap(PyObject * self_) : self(self_) {} > PyObject * self; > int f_default(std::string x) { return this->Base::f(x); } > int f(std::string x) { return call_method<int>(self, "f", x); } > }; > > BOOST_PYTHON_MODULE(mytest) > { > def("calls_f", calls_f); > class_<Base, BaseWrap>("Base") > .def("f", &Base::f, &BaseWrap::f_default); > } > > _________________ > > from mytest import * > > class Derived(Base): > def f(self, s): > return len(s) > > calls_f(Base(), 'foo') > calls_f(Derived(), 'forty-two') > > > With Boost 1.38 and Visual Studio 8 compiler I get the error: > > boost_1_38\boost\python\object\make_instance.hpp(68) : see reference to > function template instantiation > 'boost::python::objects::value_holder_back_reference<Value,Held>::value_holder_back_reference<boost::reference_wrapper<T>>(PyObject > *,A0)' being compiled > with > [ > Value=Base, > Held=BaseWrap, > T=const Base, > A0=boost::reference_wrapper<const Base> > ] > > With Boost 1.63 and Sun C++ 5.9 compiler I get the error: > > boost-1_36/boost/python/object/class_metadata.hpp", line 232: > Error: Overloading ambiguity between "static > boost::python::objects::class_metadata<Base, BaseWrap, > boost::python::detail::not_specified, > boost::python::detail::not_specified>::maybe_register_pointer_to_python(void*, > void*, void*)" > and "static boost::python::objects::class_metadata<Base, BaseWrap, > boost::python::detail::not_specified, > boost::python::detail::not_specified>::maybe_register_pointer_to_python(void*, > void*, mpl_::bool_<1>*)". > > I also tried extending the boost::python::wrapper<T> using get_override() > instead of call_method<T>(), but as it can not be constructed with a > PyObject * so the C++ base class can't be extracted from a Python > derivation. > > Has anyone managed to get this working? Any help will be gratefully > received. > > Cheers, > > Paul > > > > _______________________________________________ > Cplusplus-sig mailing list > Cplusplus-sig@python.org > http://mail.python.org/mailman/listinfo/cplusplus-sig > -- Renato Araujo Oliveira Filho _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
