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[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]
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