Re: [boost] Re: [Boost Python Library] Mixing types wrapped in different modules

From: Ullrich Koethe (koethe_at_[hidden])
Date: 2000-12-07 16:48:17

David Abrahams wrote:
> > 4. in logicmodule.cpp:
> >    - Include  "uicommon.hpp"
> >    - declare the wrapped "Window" as base of the wrapped
> >      "ResultWindow"
> >
> >     reswindow_class.get_extension_class()->
> >                          declare_base(get_window_class());
> 
> I think I see a way to do this without the get_window_class() function. I
> think it also will substantially cut down on code bloat. The usage would be
> something like:
> 
> reswindow_class.declare_base(PyObject_Getattr(PyImport_GetModule("uimodule")
> , "Window)))
> 

I tried this (with corrected function names :-), but it crashed. Perhaps
it doesn't work because Py_Initialize() must be called prior to a call
to PyImport_ImportModule("ui"). But this would create another
interpreter which isn't what we want either.

Anyway, I just realized that the function "get_window_class()" is
unnecessary because we can do the following directly within
"logicmodule.cpp":

 boost::python::detail::extension_class<Window> * window_class = 
   dynamic_cast<boost::python::detail::extension_class<Window> *>(
     boost::python::detail::class_registry<Window>::class_object());

Of course, this should be encapsulated. Encapsulation would be much
easier if the inheritance hierarchy would be changed into: 

   template <class T>
   class typed_extension_class_base : public extension_class_base 
   { ... };

   template <class T, class U = held_instance<T> >
   class extension_class
    : public python_extension_class_converters<T, U>,  functions
      public typed_extension_class_base<T>
   { ... };

Then, class_registry<T>::class_object() could return a
typed_extension_class_base<T>*, and one could simply write:

   reswindow_class.declare_base(get_class_object<Window>());

(or something similar, according to MSVC's limitations). Note that we
can't use extension_class directly because we don't know the
held_instance type if callbacks are enabled.

Ulli
-- 
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