<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <!-- Copyright David Abrahams 2006. Distributed under the Boost --> <!-- Software License, Version 1.0. (See accompanying --> <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> <html> <head> <meta name="generator" content= "HTML Tidy for Windows (vers 1st August 2002), see www.w3.org"> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" type="text/css" href="../boost.css"> <title>Boost.Python - <boost/python/return_by_value.hpp></title> </head> <body> <table border="0" cellpadding="7" cellspacing="0" width="100%" summary= "header"> <tr> <td valign="top" width="300"> <h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../boost.png" border="0"></a></h3> </td> <td valign="top"> <h1 align="center"><a href="../index.html">Boost.Python</a></h1> <h2 align="center">Header <boost/python/return_by_value.hpp></h2> </td> </tr> </table> <hr> <h2>Contents</h2> <dl class="page-index"> <dt><a href="#classes">Classes</a></dt> <dd> <dl class="page-index"> <dt><a href="#return_by_value-spec">Class <code>return_by_value</code></a></dt> <dd> <dl class="page-index"> <dt><a href="#return_by_value-spec-synopsis">Class <code>return_by_value</code> synopsis</a></dt> <dt><a href="#return_by_value-spec-metafunctions">Class <code>return_by_value</code> metafunctions</a></dt> </dl> </dd> </dl> </dd> <dt><a href="#examples">Example</a></dt> </dl> <hr> <h2><a name="classes"></a>Classes</h2> <h3><a name="return_by_value-spec"></a>Class <code>return_by_value</code></h3> <p><code>return_by_value</code> is a model of <a href= "ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a> 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.</p> <h4><a name="return_by_value-spec-synopsis"></a>Class <code>return_by_value</code> synopsis</h4> <pre> namespace boost { namespace python { struct return_by_value { template <class T> struct apply; }; }} </pre> <h4><a name="return_by_value-spec-metafunctions"></a>Class <code>return_by_value</code> metafunctions</h4> <pre> template <class T> struct apply </pre> <dl class="metafunction-semantics"> <dt><b>Returns:</b> <code>typedef <a href= "to_python_value.html#to_python_value-spec">to_python_value</a><T> type;</code></dt> </dl> <h2><a name="examples"></a>Example</h2> <h3>C++ Module Definition</h3> <pre> #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); } </pre> <h3>Python Code</h3> <pre> >>> from my_module import * >>> b = b1() # each of these calls >>> b = b2() # creates a brand >>> b = b3() # new Bar object </pre> <p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> 13 November, 2002 <!--webbot bot="Timestamp" endspan i-checksum="39359" --> </p> <p><i>© Copyright <a href= "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p> </body> </html>