[C++-sig] polymorphic object handling

[Burkhard Doliwa]

Hi all,

I have a problem wrapping a factory function to python. I have two 
abstract base classes A,B, with some child classes

A<-A1,A2,A3
B<-B1,B2,B3

every child class is either able to clone itself or to return an 
instance of the corresponding "parallel class", i.e.

A* A1::cloneA() const	yields an A1
B* A1::cloneB() const	yields an B1

A* B2::cloneA() const	yields an A2
B* B2::cloneB() const	yields an B2

and so forth. The factory function

object factoryA(const A&, bool isA) {
	return isA? object(A.cloneA()) : object(A.cloneB());
}

only returns python objects of the base class types, not the derived 
classes, i.e.

 >>> a1=A1()
 >>> factory(a1,True)
result=  A object (NOT an A1 object)

How could I create the correct derived class in such a conditional 
factory function (like the return_value_policy<manage_new_object>() case)?

Thanks,
Burkhard