bump version to 12.2.2-pve1

[ceph.git] / ceph / src / boost / libs / python / doc / reference / copy_non_const_reference.qbk

[section boost/python/copy_non_const_reference.hpp]
[section Class `copy_non_const_reference`]
`copy_non_const_reference` is a model of [link concepts.resultconverter.resultconvertergenerator_concept ResultConverterGenerator] which can be used to wrap C++ functions returning a reference-to-non-const type such that the referenced value is copied into a new Python object.
``
namespace boost { namespace python
{
    struct copy_non_const_reference
    {
        template <class T> struct apply;
    };
}}
``
[endsect]
[section Class `copy_non_const_reference` metafunctions]
``template <class T> struct apply``
[variablelist
[[Requires][`T` is `U &` for some non-const `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_non_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& get_bar() { 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_non_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]