<!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 http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" type="text/css" href="../../../../boost.css"> <title>Boost.Python - ResultConverter Concept</title> </head> <body link="#0000ff" vlink="#800080"> <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">ResultConverter Concept</h2> </td> </tr> </table> <hr> <dl class="page-index"> <dt><a href="#introduction">Introduction</a></dt> <dt><a href="#concept-requirements">Concept Requirements</a></dt> <dd> <dl class="page-index"> <dt><a href="#ResultConverter-concept">ResultConverter Concept</a></dt> <dt><a href="#ResultConverterGenerator-concept">ResultConverterGenerator Concept</a></dt> </dl> </dd> </dl> <h2><a name="introduction"></a>Introduction</h2> <p>A ResultConverter for a type <code>T</code> is a type whose instances can be used to convert C++ return values of type <code>T</code> <code>to_python</code>. A ResultConverterGenerator is an MPL unary metafunction class which, given the return type of a C++ function, returns a ResultConverter for that type. ResultConverters in Boost.Python generally inspect library's registry of converters to find a suitable converter, but converters which don't use the registry are also possible. <h2><a name="concept-requirements"></a>Concept Requirements</h2> <h3><a name="ResultConverter-concept"></a>ResultConverter Concept</h3> <p>In the table below, <code><b>C</b></code> denotes a ResultConverter type for a type <b><code>R</code></b> , <code><b>c</b></code> denotes an object of type <code><b>C</b></code> , and <code><b>r</b></code> denotes an object of type <code><b>R</b></code>. <table summary="ResultConverter expressions" border="1" cellpadding="5"> <tr> <td><b>Expression</b></td> <td><b>Type</b></td> <td><b>Semantics</b></td> </tr> <tr> <td valign="top"><code>C c;</code></td> <td> <td>Constructs a <code>C</code> object. </tr> <tr> <td valign="top"><code>c.convertible()</code></td> <td>convertible to <code>bool</code></td> <td><code>false</code> iff no conversion from any <code>R</code> value to a Python object is possible.</td> </tr> <tr> <td valign="top"><code>c(r)</code></td> <td>convertible to <code>PyObject*</code></td> <td>A pointer to a Python object corresponding to <code>r</code>, or <code>0</code> iff <code>r</code> could not be converted <code>to_python</code>, in which case <a href="http://www.python.org/doc/current/api/exceptionHandling.html#l2h-71">PyErr_Occurred</a> should return non-zero.</td> </tr> <tr> <td valign="top"><code>c.get_pytype()</code></td> <td><code>PyTypeObject const*</code></td> <td>A pointer to a Python Type object corresponding to result of the conversion, or <code>0</code>. Used for documentation generation. If <code>0</code> is returned the generated type in the documentation will be <b>object</b> .</td> </tr> </table> <h3><a name="ResultConverterGenerator-concept"></a>ResultConverterGenerator Concept</h3> <p>In the table below, <code><b>G</b></code> denotes a ResultConverterGenerator type and <code><b>R</b></code> denotes a possible C++ function return type. <table summary="ResultConverterGenerator expressions" border="1" cellpadding="5"> <tr> <td><b>Expression</b></td> <td><b>Requirements</b></td> </tr> <tr> <td valign="top"><code>G::apply<R>::type</code></td> <td>A ResultConverter type for <code>R</code>.</td> </table> <hr> <p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> 09 May, 2002 <!--Luann's birthday! --> <!--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>Permission to copy, use, modify, sell and distribute this software is granted provided this copyright notice appears in all copies. This software is provided "as is" without express or implied warranty, and with no claim as to its suitability for any purpose. </body> </html>