[C++-sig] Wrapping a base class' method

[Ralf W. Grosse-Kunstleve]

Write a thin wrapper and .add_property that, e.g. (untested)

int get_base_i_directly(my_class const& self) { return self.get_base_i(); }
...

      .add_property("basei",    make_function(get_base_i_directly))

This way Boost.Python only "sees" my_class in the signature.

----- Original Message ----
From: "bernhard.maeder at zkb.ch" <bernhard.maeder at zkb.ch>
To: c++-sig at python.org
Sent: Sunday, November 19, 2006 11:30:28 PM
Subject: [C++-sig] Wrapping a base class' method


Hello all



I'm trying to export some base class' methods  with the derived class directly. See the following code:



// -----------------------------------------------------

#include <boost/python.hpp>



struct my_base_class

{

    int const & get_base_i() const

    {

        return i_;

    }

    int i_;

};



struct my_class

  : my_base_class

{

    int const & get_i() const

    {

        return i_;

    }

    

    int i_;    

};



using namespace boost::python;



BOOST_PYTHON_MODULE(_test)

{

    class_<my_class>("MyClass")

      .add_property("i",        make_function(&my_class::get_i,      return_value_policy<copy_const_reference>()))

      .add_property("basei",    make_function(&my_class::get_base_i, return_value_policy<copy_const_reference>()))

      ;        

}



// -----------------------------------------------------



Now python throws the following at me:



h[ 1] >>> from _test import *

h[ 1] >>> MyClass().basei

Traceback (most recent call last):

  File "<stdin>", line 1, in ?

Boost.Python.ArgumentError: Python argument types in

    None.None(MyClass)

did not match C++ signature:

    None(my_base_class {lvalue})



So, my question is: Am I not supposed to do this at all? The same seems to work flawlessly when returning by value instead of by reference....



Thanks for your input



Bernhard

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