[section boost/python/copy_const_reference.hpp]

[section Class `copy_const_reference`]

`copy_const_reference` is a model of [link concepts.resultconverter.resultconvertergenerator_concept 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.

``

namespace boost { namespace python

{

struct copy_const_reference

{

template <class T> struct apply;

};

}}

``

[endsect]

[section Class `copy_const_reference` metafunctions]

``template <class T> struct apply``

[variablelist

[[Requires][`T` is `U const&` for some `U`.]]

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

]

[endsect]

[section 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

``

[endsect]

[endsect]