[C++-sig] Exposing simple polymorphism with boost python

[Erik Türke]

Hi Python-Experts :-)


i am starting to get really frustrated trying to expose a simple C++
polymorphism to python with boost::python.
I do have the following structure in C++:

    struct Base {
        int typeID;
    };

    struct Derived : public Base {
        int derivedProperty;
    }

    //and some more from base derived types....

    Base *returnSomethingDerivedFromBase(...) {
        Derived *ret = new Derived;
        ret->derivedProperty = 1234;
        return ret;
    }

    BOOST_PYTHON_MODULE(foo)
    {
        class_<Base>("Base")
            .add_property("baseProperty", &Base::baseProperty);

        class_<Derived, bases<Base> >("Derived")
            .add_property("derivedProperty", &Derived::derivedProperty);

        def("returnSomethingDerivedFromBase",
returnSomethingDerivedFromBase);
    }


And in Python i just want to have the following:

    object = returnSomethingFromDerived() #object is of type Base
    if object.typeID = 1:
        #here i want to cast to Derived and access "derivedProperty"
        #but this is not working :-( :
        object.__class__ = Derived

Is there a way to accomplish this at all? Or isn´t this possible as it
would be in C++ ?

Thanks a lot for your help!!
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