[C++-sig] python extended object to native c++ pointer

[Mark Chandler]

Im toying around with the idea to use python as an embedded scripting 
language for a project im working on and have got most things working. 
However i cant seem to be able to convert a python extended object back 
into a native c++ pointer.

So this is my class:
   class CGEGameModeBase
   {
   public:
       virtual void FunctionCall()=0;
       virtual const char* StringReturn()=0;
   };
   
   class CGEPYGameMode : public CGEGameModeBase, public 
boost::python::wrapper<CGEPYGameMode>
   {
   public:
       virtual void FunctionCall()
       {
           if (override f = this->get_override("FunctionCall"))
               f();
       }
   
       virtual const char* StringReturn()
       {
           if (override f = this->get_override("StringReturn"))
               return f();
   
           return "FAILED TO CALL";
       }
   };

Boost wrapping:

   BOOST_PYTHON_MODULE(GEGameMode)
   {
       class_<CGEGameModeBase, boost::noncopyable>("CGEGameModeBase", 
no_init);
   
       class_<CGEPYGameMode, bases<CGEGameModeBase> >("CGEPYGameMode", 
no_init)
           .def("FunctionCall", &CGEPYGameMode::FunctionCall)
           .def("StringReturn", &CGEPYGameMode::StringReturn);
   }

and the python code:

   import GEGameMode
   
   def Ident():
       return "Alpha"
       
   def NewGamePlay():
       return "NewAlpha"
   
   
   def NewAlpha():
       import GEGameMode
       import GEUtil
   
       class Alpha(GEGameMode.CGEPYGameMode):
           def __init__(self):
               print "Made new Alpha!"
   
           def FunctionCall(self):
               GEUtil.Msg("This is function test Alpha!")
   
           def StringReturn(self):
               return "This is return test Alpha!"
               
       return Alpha()


Now i can call the first to functions fine by doing this:

   const char* ident = extract< const char* >( GetLocalDict()["Ident"]() );
   const char* newgameplay = extract< const char* >( 
GetLocalDict()["NewGamePlay"]() );

   printf("Loading Script: %s\n", ident);
   CGEPYGameMode* m_pGameMode = extract< CGEPYGameMode* >( 
GetLocalDict()[newgameplay]() );


However when i try and convert the Alpha class back to its base class 
(last line above) i get an boost error:

   TypeError: No registered converter was able to extract a C++ pointer 
to type class CGEPYGameMode from this Python object of type Alpha

I have done alot of searching on the net but cant work out how to 
convert the Alpha object into its base class pointer. I could leave it 
as an object but rather have it as a pointer so some non python aware 
code can use it. Any ideas?


Better Formatted version: 
http://stackoverflow.com/questions/1355187/python-object-to-native-c-pointer

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