[prev in list] [next in list] [prev in thread] [next in thread] 

List:       python-cpp-sig
Subject:    [C++-sig] Making Boost.Python understand DerivedSafe
From:       caustin () gmail ! com (Chad Austin)
Date:       2004-06-17 5:31:04
Message-ID: 2096514e0406170112773a0e76 () mail ! gmail ! com
[Download RAW message or body]

(I am not yet subscribed to the list...  it seems mailman is having
trouble sending me the authorization.  Please CC me on replies.. 
Thanks.)

Hi all,

I just started using Boost.Python to embed Python in a project of
mine.  I spent a couple days evaluating, testing, and studying, but it
seems to have paid off!  Great job on making such a time-saving
library!

I am wrapping an internally refcounted class called CutScene. 
CutScene objects are referenced by RefPtr<CutScene> smart pointers,
typedef'd as CutScenePtr.  I export the class with:

class_<CutScene, CutScenePtr>("CutScene").def /*etc*/;

So far, so good.  The problem comes about when I want to pass a
CutScenePtr into object::operator() to call a function.  If I pass a
CutScenePtr object in, it says something about reject_raw_object_ptr:

d:\Projects\empyrean\empyrean\third-party-vc7\include\boost\python\converter\arg_to_python.hpp(244)
: error C2784: 'void
boost::python::converter::detail::reject_raw_object_ptr(T *)' : could
not deduce template argument for 'T1 *' from 'pyr::RefPtr<T>'
        with
        [
            T=pyr::CutScene
        ]

If I pass the result of CutScenePtr::get() into operator() I get a
runtime error about Boost.Python not knowing how to convert
RefDerivedSafe<T>* to a Python object.  This makes sense, because
RefPtr's implicit conversion operator, operator->, and get() all
return RefDerivedSafe<T>*. (RefDerivedSafe<T> is a special class
derived from T that prevents C++ clients from accidentally calling
delete, ref(), or unref() on a smart pointer. This techique is used in
both ATL and nsCOMPtr in Mozilla).

Here's my question:  Is there a way to tell Boost.Python that
ptr(someCutScenePtr) is valid and should be equivalent to
ptr(someCutScenePtr.get()) and/or that RefDerivedSafe<T>* can be
implicitly converted to T*?  I've tried several different things, and
nothing seems to work...

I'm currently using Boost 1.31 with both gcc 3.3.1 and VS.NET 2003.

Many thanks,
Chad

[prev in list] [next in list] [prev in thread] [next in thread]