[C++-sig] Smart Pointers in Boost.Python with AutomaticDereferencing

[Ralf W. Grosse-Kunstleve]

No, sorry.

Very wild idea: can your smart pointer be converted both ways to/from a boost::shared_ptr? And are all your smart pointer objects passed by value
or const&? Then maybe a custom rvalue converter could do the trick.

I hope someone else with actual experience in this area will be able
to help.

Ralf

----- Original Message ----
From: "Bilokon, Paul" <paul.bilokon at lehman.com>
To: Development of Python/C++ integration <c++-sig at python.org>
Sent: Monday, May 19, 2008 10:18:38 AM
Subject: Re: [C++-sig] Smart Pointers in Boost.Python with AutomaticDereferencing


Hi Ralf,

Many thanks for your reply.

Unfortunately, I do have a custom "smart" pointer and it would be very
difficult to convert it.

Do you know if there are any code examples for custom smart pointers?

Many thanks,
Paul

-----Original Message-----
From: c++-sig-bounces at python.org [mailto:c++-sig-bounces at python.org] On
Behalf Of Ralf W. Grosse-Kunstleve
Sent: Monday, May 19, 2008 5:52 PM
To: Development of Python/C++ integration
Subject: Re: [C++-sig] Smart Pointers in Boost.Python with
AutomaticDereferencing

Boost.Python has special support for boost::shared_ptr<>. E.g. this
should do what you want (untested):

  class_<A, shared_ptr<A> >("A")

It is more difficult only if you have your own smart pointers.

Ralf

----- Original Message ----
From: "Bilokon, Paul" <paul.bilokon at lehman.com>
To: Development of Python/C++ integration <c++-sig at python.org>
Sent: Monday, May 19, 2008 5:30:59 AM
Subject: [C++-sig] Smart Pointers in Boost.Python with Automatic
Dereferencing


Hi all,

I'm trying to find an authoritative resource on exposing functions that
return smart pointers using Boost.Python.

So far my best example is this:

http://wiki.python.org/moin/boost.python/PointersAndSmartPointers

However, I find the need to explicitly dereference the pointer in Python
deeply unsatisfactory:

print (+an_A).hello()

This is essentially C++ programming in Python. The whole purpose of the
exercise is to avoid the need for explicit memory management!

Is there another method that will simply allow me to call

print an_A.hello()

Many thanks for your help!

Best wishes,
Paul


P.S. Just for your information I'll paste the C++ code:

#include <boost/shared_ptr.h>
using namespace boost;

struct A {
    shared_ptr<A> create () { return shared_ptr<A>(new A); }
    std::string   hello  () { return "Just nod if you can hear me!"; }
};

BOOST_PYTHON_MODULE(shared_ptr)
{
    class_<A>("A",init<>())
        .def("create",&A::create,return_value_policy<return_by_value>())
        .staticmethod("create")
        .def("hello",&A::hello)
        ;

    class_< shared_ptr<A> >("A_ptr", init<const shared_ptr<A>& >())

.def("__pos__",&boost::shared_ptr<A>::get,return_internal_reference<>())
        ;
}

And the sample Python program:

from shared_ptr import *
an_A = A_ptr.create()
print (+an_A).hello()
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