Boost C++ Libraries

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C++ Boost

Boost.Python

Header <boost/python/copy_const_reference.hpp>


Contents

Classes
Class copy_const_reference
Class copy_const_reference synopsis
Class copy_const_reference metafunctions
Example

Classes

Class copy_const_reference

copy_const_reference is a model of ResultConverterGenerator which can be used to wrap C++ functions returning a reference-to-const type such that the referenced value is copied into a new Python object.

Class copy_const_reference synopsis

namespace boost { namespace python
{
    struct copy_const_reference
    {
        template <class T> struct apply;
    };
}}

Class copy_const_reference metafunctions

template <class T> struct apply
Requires: T is U const& for some U.
Returns: typedef to_python_value<T> type;

Example

C++ Module Definition

#include <boost/python/module.hpp>
#include <boost/python/class.hpp>
#include <boost/python/copy_const_reference.hpp>
#include <boost/python/return_value_policy.hpp>

// classes to wrap
struct Bar { int x; }

struct Foo {
   Foo(int x) : { b.x = x; }
   Bar const& get_bar() const { return b; }
 private:
   Bar b;
};

// Wrapper code
using namespace boost::python;
BOOST_PYTHON_MODULE(my_module)
{
    class_<Bar>("Bar");

     class_<Foo>("Foo", init<int>())
        .def("get_bar", &Foo::get_bar
            , return_value_policy<copy_const_reference>())
       ;
}

Python Code

>>> from my_module import *
>>> f = Foo(3)         # create a Foo object
>>> b = f.get_bar()    # make a copy of the internal Bar object

Revised 13 November, 2002

© Copyright Dave Abrahams 2002. All Rights Reserved.