[C++-sig] Can't call injected method taking SmartPtr with derived object... (original) (raw)

Alex Mohr amohr at pixar.com
Mon Dec 19 20:56:11 CET 2005

I'm having a bit of trouble with inheritance and injected methods. Here's a small example. In this example, SmartPtr is a custom smart pointer much like boost::shared_ptr.

class Base { public: virtual ~Base() {} };

class Derived : public Base { public: virtual ~Derived() {} static SmartPtr GetAsBase(SmartPtr const &p) { return SmartPtr(p); } string derivedMethod() { return "Derived Method"; } }; static SmartPtr newDerived() { ...makes a new derived... }

static string injectedMethod(SmartPtr const &self) { return "Injected Method"; }

BOOST_PYTHON_MODULE(foo) { class_<Base, SmartPtr >("Base", no_init); class_<Derived, SmartPtr, bases > ("Derived", no_init) .def("init", make_constructor(newDerived)) .def("derivedMethod", &Derived::derivedMethod) .def("injectedMethod", injectedMethod) .def("GetAsBase", &Derived::GetAsBase).staticmethod("GetAsBase") ; }

d = Derived() d.derivedMethod() 'Derived Method' d.injectedMethod() 'Injected Method' b = Derived.GetAsBase(d) type(b) <class 'foo.Derived'> b.derivedMethod() 'Derived Method' b.injectedMethod() Traceback (most recent call last): File "", line 1, in ? Boost.Python.ArgumentError: Python argument types in Derived.injectedMethod(Derived) did not match C++ signature: injectedMethod(SmartPtr)

Here are some observations. 1) This actually works right if I make the C++ injectedMethod take 'Derived const &' rather than 'SmartPtr const &'. 2) The whole example works fine as-is if I use boost::shared_ptr rather than my own custom smart pointer.

Any help is greatly appreciated.

Thanks,

Alex

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