###

# Boost.Python

## Header <boost/python/return_by_value.hpp>

## Contents

Classes
  Class `return_by_value`
    Class `return_by_value` synopsis
    Class `return_by_value` metafunctions
Example

## Classes

### Class `return_by_value`

`return_by_value` is a model of 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.

#### Class `return_by_value` synopsis

    namespace boost { namespace python
    {
        struct return_by_value
        {
            template <class T> struct apply;
        };
    }}

#### Class `return_by_value` metafunctions

    template <class T> struct apply

Returns: `typedef to_python_value<T> type;`

## Example

### C++ Module Definition

    #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

Revised 13 November, 2002

© Copyright Dave Abrahams 2002.