[section boost/python/return_by_value.hpp]

[section Class `return_by_value`]

`return_by_value` is a model of [link concepts.resultconverter.resultconvertergenerator_concept ResultConverterGenerator] which can be used to wrap C++ functions returning any reference or value type such that the return value is copied into a new Python object.

``

namespace boost { namespace python

{

struct return_by_value

{

template <class T> struct apply;

};

}}

``

[endsect]

[section Class `return_by_value` metafunctions]

``template <class T> struct apply``

[variablelist

[[Returns][`typedef to_python_value<T> type;`]]

]

[endsect]

[section Example]

In C++:

``

#include <boost/python/module.hpp>

#include <boost/python/class.hpp>

#include <boost/python/return_by_value.hpp>

#include <boost/python/return_value_policy.hpp>

// classes to wrap

struct Bar { };

Bar global_bar;

// functions to wrap:

Bar b1();

Bar& b2();

Bar const& b3();

// Wrapper code

using namespace boost::python;

template <class R>

void def_void_function(char const* name, R (*f)())

{

def(name, f, return_value_policy<return_by_value>());

}

BOOST_PYTHON_MODULE(my_module)

{

class_<Bar>("Bar");

def_void_function("b1", b1);

def_void_function("b2", b2);

def_void_function("b3", b3);

}

``

Python code:

``

>>> from my_module import *

>>> b = b1() # each of these calls

>>> b = b2() # creates a brand

>>> b = b3() # new Bar object

``

[endsect]

[endsect]