class Interface{
public:
Clock* clock;
Camera* camera;
...
};
Interface systems; //this is global and extern
How do I expose my Interface instance to python using boost? I will never need to create a new instance, I just need to use this one.
I thought about doing object o = (class_(...))(); but that only exposes the class, not the instance.
Thanks.
Dustin
object o = object( systems );/* the next line is to call a function with your objectinstance as parameter. if you want the object to be in theglobal namespace of the particular module, try adding it to themodule's global dictionary, and then in each function doing thewhole 'global systems' dance to get the global variable. I'mnot sure if that approach will work however, but I know the onebelow will. I'm NOT however, sure that that's the rightsyntax, I just wrote it up from memory here, so check it out. */PyObject_CallFunction( YourFunc, "O", object.ptr() );from __future__ import generators #python 2.3 won't work with boost yetprint "test_interface.py> loaded script"import katanaprint "after import katana"def main(): print "script> Main" print katana.GetInterface() #prints "<katana.Interface object at 0x099868B4<" print "never gets here" yield None 
ython ststic module katana definition#ifndef __PYKATANA_HPP#define __PYKATANA_HPP#include <boost/python.hpp>//#include <boost/python/object.hpp>//#include <boost/python/def.hpp>using namespace boost::Python;#include "interface.hpp"extern Interface systems;object GetInterface() {return object(systems);}BOOST_PYTHON_MODULE(katana){ class_<Interface>( "Interface", init<>() ) .def_readonly( "clock", &Interface::clock ); class_<Clock>( "Clock", init<>() ) .def( "GetTimeSincecLastTick", &Clock::GetTimeSinceLastTick ) .def( "GetTime", &Clock::GetTime ) .def( "GetExactTime", &Clock::GetExactTime ) .def( "GetAvgFps", &Clock::GetAvgFps ) .def( "GetExactFps", &Clock::GetExactFps ) .def( "GetElapsedTimeSec", &Clock::GetElapsedTimeSec ) .def( "GetStartTime", &Clock::GetStartTime ) .def( "GetFramecount", &Clock::GetFramecount ); //def( "GetInterface", GetInterface, return_value_policy<reference_existing_object>() ); //this doesn't compile, but I think this is the key to my problem def( "GetInterface", GetInterface );}#endif //__PYKATANA_HPP// here's my classclass CFoo{private: // some data member char Bar[ 32 ]public: // some functions... void Set( char* NewBar ); const char* Get();};// here's my static objectstatic CFoo myFoo;// and here's a function to return the object.// in my engine, I have this located inside the class// (I use a variant of superpig's singleton class in his// enginuity articles), though you can have it outside as well,// it doesn't make a differenceCFoo& getFoo(){ return myFoo;}// here's our boost definition. notice how if a function is// either static (and located inside a class) or just a function,// you just put a 'def' without putting a class_<> template.// we use 'reference_existing_object' because it's a singleton// and we don't want copies of it floating around (though boost// doesn't do a very good job of explaining these return policies// does it?)BOOST_PYTHON_MODULE(foo){ class_<CFoo>( "CFoo", init<>() ) .def( "Set", &CFoo::Set ) # this COULD be a 'property'... .def( "Get", &CFoo::Get ) # since it's 'const', we don't need a return policy ; def( "getFoo", getFoo, return_value_policy<reference_existing_object>() );}And that's how you expose the class to python. Now don't forget, if you're embedding Python in the same application as this is being exposed (i.e. you're NOT exporting a seperate DLL), remember to 'initfoo' in your main() function so Python can see it. You only use the Boost :: Python 'object' class to encapsulate PyObject*'s, like when you're trying to pass objects into functions as arguments. If you're returning objects from functions then you don't have to worry about the conversion.Oh yeah, and for the Python script file, you'd have something like this (just made it up, don't expect it to run): import foomyFoo = foo.getFoo()myFoo.Set( "Chris Wuz Here" )print myFoo.Get() # should print 'Chris Wuz Here'# get the clockmyClock = systems.getClock()...# use the clockmyClock.Blah()static CFoo myFoo; extern static Interface systems; 
extern Interface systems;Interface & GetInterface() {return systems;}BOOST_PYTHON_MODULE(katana){ class_<Interface>( "Interface", init<>() ) .def_readonly( "clock", &Interface::clock ) //.def_readonly( "camera", &Interface::camera ) ; class_<Clock>( "Clock", init<>() ) .def( "GetTimeSincecLastTick", &Clock::GetTimeSinceLastTick ) .def( "GetTime", &Clock::GetTime ) .def( "GetExactTime", &Clock::GetExactTime ) .def( "GetAvgFps", &Clock::GetAvgFps ) .def( "GetExactFps", &Clock::GetExactFps ) .def( "GetElapsedTimeSec", &Clock::GetElapsedTimeSec ) .def( "GetStartTime", &Clock::GetStartTime ) .def( "GetFramecount", &Clock::GetFramecount ); def( "GetInterface", GetInterface, return_value_policy<reference_existing_object>() ); //def( "GetInterface", GetInterface );}Compiling...script.cppc:\utilities\boost_1_30_0\boost\python\object\inheritance.hpp(48) : warning C4541: 'dynamic_cast' used on polymorphic type 'class Clock' with /GR-; unpredictable behavior may result c:\utilities\boost_1_30_0\boost\python\object\inheritance.hpp(46) : while compiling class-template member function 'struct std::pair<void *,struct boost::python::type_info> __cdecl boost::python::objects::polymorphic_id_generator<class Clock>::execute(void *)'c:\utilities\boost_1_30_0\boost\python\object\inheritance.hpp(48) : warning C4541: 'typeid' used on polymorphic type 'class Clock' with /GR-; unpredictable behavior may result c:\utilities\boost_1_30_0\boost\python\object\inheritance.hpp(46) : while compiling class-template member function 'struct std::pair<void *,struct boost::python::type_info> __cdecl boost::python::objects::polymorphic_id_generator<class Clock>::execute(void *)'c:\utilities\boost_1_30_0\boost\mpl\if.hpp(88) : fatal error C1076: compiler limit : internal heap limit reached; use /Zm to specify a higher limit c:\utilities\boost_1_30_0\boost\mpl\if.hpp(88) : see reference to class template instantiation 'boost::mpl::if_c<0,struct boost::python::detail::specify_a_return_value_policy_to_wrap_functions_returning<void>,struct boost::python::to_python_value<void> >::answer<`template-parameter513'>' being compiled c:\utilities\boost_1_30_0\boost\python\default_call_policies.hpp(59) : see reference to class template instantiation 'boost::mpl::if_c<0,struct boost::python::detail::specify_a_return_value_policy_to_wrap_functions_returning<void>,struct boost::python::to_python_value<void> >' being compiled c:\utilities\boost_1_30_0\boost\mpl\aux_\preprocessed\msvc60\apply.hpp(41) : see reference to class template instantiation 'boost::python::default_result_converter::apply<void>' being compiled c:\utilities\boost_1_30_0\boost\mpl\aux_\preprocessed\msvc60\apply.hpp(54) : see reference to class template instantiation 'boost::mpl::aux::msvc_apply1<struct boost::python::default_result_converter>::result_<void>' being compiled c:\utilities\boost_1_30_0\boost\python\detail\caller.hpp(53) : see reference to class template instantiation 'boost::mpl::apply1<struct boost::python::default_result_converter,void>' being compiled c:\utilities\boost_1_30_0\boost\python\detail\caller.hpp(148) : see reference to class template instantiation 'boost::python::detail::select_result_converter<struct boost::python::default_call_policies,void>' being compiled c:\utilities\boost_1_30_0\boost\python\detail\caller.hpp(145) : while compiling class-template member function 'struct _object *__thiscall boost::python::detail::caller_arity<1>::impl<void (__cdecl*)(struct _object *),struct boost::python::detail::args_from_python,struct boost::python::default_call_policies,struct boost::mpl::list2<void,struct _object *> >::operator ()(struct _object *,struct _object *)'Error executing cl.exe.def( "GetInterface", GetInterface, return_value_policy() ); 
run_string("import katana");run_string("katana.clock=katana.GetClock()"); 