###  | # 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.