Boost Python and shared_ptr upcast

Question

---

Sample code for dll/pyd:

#include <boost/python.hpp>
#include <iostream>

class Base
{
public: Base() {}
public: int getValue() { return 1; }
};

typedef boost::shared_ptr<Base> BasePtr;

class ParentA : public Base
{   
public: ParentA() : Base() {}
};

typedef boost::shared_ptr<ParentA> ParentAPtr;

class Collector
{
public: Collector() {}
public: void addParent(BasePtr& parent)
{
    std::cout << parent->getValue() << std::endl;
}
};

typedef boost::shared_ptr<Collector> CollectorPtr;

ParentAPtr createParentA()
{
return ParentAPtr(new ParentA());
};

BOOST_PYTHON_MODULE(hello)
{
boost::python::class_<Base, BasePtr, boost::noncopyable>("Base",
        boost::python::no_init)
        .def("getValue", &Base::getValue)
;

boost::python::class_<ParentA, ParentAPtr, boost::python::bases<Base>>("ParentA")
;

boost::python::implicitly_convertible< ParentAPtr, BasePtr >();

boost::python::def("createParentA", createParentA);

boost::python::class_<Collector, CollectorPtr>("Collector")
    .def("addParent", &Collector::addParent)
;
}

---

example code to test it in Python console:

import hello
p = hello.createParentA()
c = hello.Collector()
c.addParent(p)

---

Initial post with fake code:

I'm having some problems in having Boost Python to upcast a shared_ptr from Python.

class Base() {...};
class ParentA(): public Base {...};
class ParentB(): public Base {...};

typedef boost::shared_ptr<Base> BasePtr;
typedef boost::shared_ptr<Parent> ParentPtr;

class Collector() 
{
  void addParent(BasePtr& parent) {...}
}
typedef boost::shared_ptr<Collector> CollectorPtr;

BOOST_PYTHON_MODULE(PythonModule)
{
 boost::python::class_<Collector, CollectorPtr>("Collector")
  .def("addParent", &Collector::addParent)


 boost::python::class_<Base, BasePtr, boost::noncopyable>("Base", 
            boost::python::no_init)
 ...
 ;

 boost::python::class_<ParentA, ParentAPtr, 
            boost::python::bases<Base>>("ParentA", 
        boost::python::init<>())
 ...
 ;

 boost::python::implicitly_convertible< ParentAPtr, BasePtr >();
}

And in Python we do:

from PythonModule import *
p = ParentA()
c = Collector()
c.addParent(p) # Fails here because no upcast is happening. 

Any ideas on how I can make this work?

Compiled on VS2008, with BOOST 1.44 and Python 3.0.

Thanks,

Answer 1

Ok... while preparing the real sample code I came out with the solution. The problem is in the Collector.addParent(BasePtr& parent). It seems that Boost Python does not like it to be a reference. Changing it to be Collector.addParent(BasePtr parent) fixes it. Thanks for looking into it.