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<!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_value_policy.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_value_policy.hpp></h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dd>
<dl class="page-index">
<dt><a href="#return_value_policy-spec">Class Template
<code>return_value_policy</code></a></dt>
<dd>
<dl class="page-index">
<dt><a href="#return_value_policy-spec-synopsis">Class Template
<code>return_value_policy</code> synopsis</a></dt>
</dl>
</dd>
</dl>
</dd>
<dt><a href="#examples">Example</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<code>return_value_policy</code> instantiations are simply models of <a
href="CallPolicies.html">CallPolicies</a> which are composed of a <a
href=
"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a>
and optional <code>Base</code> <a href=
"CallPolicies.html">CallPolicies</a>.
<h2><a name="classes"></a>Classes</h2>
<h3><a name="return_value_policy-spec"></a>Class template
<code>return_value_policy</code></h3>
<table border="1" summary="return_value_policy template parameters">
<caption>
<b><code>return_value_policy</code> template parameters</b>
</caption>
<tr>
<th>Parameter</th>
<th>Requirements</th>
<th>Default</th>
</tr>
<tr>
<td><a href=
"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a></td>
<td>A model of <a href=
"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a>.</td>
</tr>
<tr>
<td><code>Base</code></td>
<td>A model of <a href="CallPolicies.html">CallPolicies</a></td>
<td><code><a href=
"default_call_policies.html#default_call_policies-spec">default_call_policies</a></code></td>
</tr>
</table>
<h4><a name="return_value_policy-spec-synopsis"></a>Class template
<code>return_value_policy</code> synopsis</h4>
<pre>
namespace boost { namespace python
{
template <class ResultConverterGenerator, class Base = default_call_policies>
struct return_value_policy : Base
{
typedef ResultConverterGenerator result_converter;
};
}}
</pre>
<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/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>())
;
}
</pre>
<h3>Python Code</h3>
<pre>
>>> from my_module import *
>>> f = Foo(3) # create a Foo object
>>> b = f.get_bar() # make a copy of the internal 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>