[C++-sig] CXX : getting a C++ object

[Benjamin Golinvaux]

I have found the solution to my problem. 
The base class of the user-defined c++ 
python extension type provides
a static bool check( PyObject* ) method
that checks whether the object is of its
kind.

// somewhere :
class MyExtensionType : public Py::PythonExtension<MyExtensionType>
{
...
}

//somewhere else
Object someFunctionExposedToPython(const Tuple &a)
{
  Object o = a[0]; 
  if(MyExtensionType::check(o.ptr())) {
    MyExtensionType* cppObj = static_cast<MyExtensionType*>(cppObj);
    // do something with cppObj
  }
  else {
    // it's not a MyExtensionType*, do something else
  }
}

(of course this isn't needed for MyExtensionType methods
where "this" is automatically set correctly)
 
this is exactly what i needed. hope this can
help someone else (although it seems everyone
here uses boost :)

Benjamin


-----Message d'origine-----
De : c++-sig-bounces at python.org [mailto:c++-sig-bounces at python.org] De la part de Benjamin Golinvaux
Envoyé : Saturday, August 28, 2004 11:48 PM
À : Development of Python/C++ integration
Objet : [C++-sig] CXX : getting a C++ object

Hello

I would like to wrap a small C++ library using CXX.

I would like to know how I can extract the C++ instance from a PyObject passed to a function. Can I assume, after a correct type check, that I can safely downcast the PyObject ? (or using dynamic_cast ?)

If I can't (or don't want to) use dynamic_cast , what could then be the best way to test that a PyObject is actually from a wrapped C++ "python type" class ?  (sorry I'm a beginner in the Python C API)

Thanks for your help

Benjamin Golinvaux 

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