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| <title>Boost.Python - <boost/python/to_python_indirect.hpp></title> |
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| <h3><a href="../../../../index.htm"><img height="86" width="277" alt= |
| "C++ Boost" src="../../../../boost.png" border="0"></a></h3> |
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| <td valign="top"> |
| <h1 align="center"><a href="../index.html">Boost.Python</a></h1> |
| |
| <h2 align="center">Header <boost/python/to_python_indirect.hpp></h2> |
| </table> |
| <hr> |
| |
| <h2>Contents</h2> |
| |
| <dl class="page-index"> |
| <dt><a href="#introduction">Introduction</a> |
| |
| |
| <dt><a href="#classes">Classes</a> |
| |
| <dd> |
| <dl class="page-index"> |
| <dt><a href="#to_python_indirect-spec">Class Template <code>to_python_indirect</code></a> |
| |
| <dd> |
| <dl class="page-index"> |
| |
| <dt><a href="#to_python_indirect-spec-synopsis">Class Template |
| <code>to_python_indirect</code> synopsis</a> |
| |
| <dt><a href="#to_python_indirect-spec-observers">Class Template |
| <code>to_python_indirect</code> observer functions</a> |
| |
| <dt><a href="#to_python_indirect-spec-statics">Class Template |
| <code>to_python_indirect</code> static functions</a> |
| </dl> |
| </dl> |
| |
| <dt><a href="#examples">Example</a> |
| </dl> |
| <hr> |
| |
| <h2><a name="introduction"></a>Introduction</h2> |
| |
| <code><boost/python/to_python_indirect.hpp></code> supplies |
| a way to construct new Python objects that hold wrapped C++ class |
| instances via a pointer or smart pointer. |
| |
| <h2><a name="classes"></a>Classes</h2> |
| |
| <h3><a name="to_python_indirect-spec"></a>Class template <code>to_python_indirect</code></h3> |
| <p>Class template <code>to_python_indirect</code> converts objects |
| of its first argument type to python as extension class instances, using the ownership policy provided by its 2nd argument. |
| |
| <p> |
| |
| |
| <table border="1" summary="to_python_indirect template parameters"> |
| <caption> |
| <b><code>to_python_indirect</code> Requirements</b><br> |
| |
| In the table below, <b><code>x</code></b> denotes an object of |
| type <code>T</code>, <b><code>h</code></b> denotes an |
| object of type |
| <code>boost::python::objects::instance_holder*</code>, and |
| <b><code>p</code></b> denotes an object of type |
| <code>U*</code>. |
| |
| </caption> |
| <tr> |
| <th>Parameter |
| |
| <th>Requirements |
| |
| <th>Description |
| |
| <tr> |
| <td><code>T</code> |
| |
| <td>Either <code>U</code> <i>cv</i><code>&</code> |
| (where <i>cv</i> is any optional cv-qualification) or a <a |
| href="Dereferenceable.html">Dereferenceable</a> type such that |
| <code>*x</code> is convertible to <code>U const&</code>, where |
| <code>U</code> is a class type. |
| |
| <td>A type deferencing a C++ class exposed to Python using |
| class template <code><a |
| href="class.html#class_-spec">class_</a></code>. |
| |
| <tr> |
| <td><code>MakeHolder</code> |
| |
| <td>h = MakeHolder::execute(p); |
| |
| <td>A class whose static <code>execute()</code> creates an |
| <code>instance_holder</code>. |
| |
| </table> |
| |
| Instantiations of <code>to_python_indirect</code> are models of <a |
| href="ResultConverter.html#ResultConverter-concept">ResultConverter</a>. |
| |
| |
| <h4><a name="to_python_indirect-spec-synopsis"></a>Class template <code>to_python_indirect</code> synopsis</h4> |
| <pre> |
| namespace boost { namespace python |
| { |
| template <class T, class MakeHolder> |
| struct to_python_indirect |
| { |
| static bool convertible(); |
| PyObject* operator()(T ptr_or_reference) const; |
| private: |
| static PyTypeObject* type(); |
| }; |
| }} |
| </pre> |
| |
| <h4><a name="to_python_indirect-spec-observers"></a>Class template <code>to_python_indirect</code> observers</h4> |
| <pre> |
| PyObject* operator()(T x) const; |
| </pre> |
| |
| <dl class="function-semantics"> |
| |
| <dt><b>Requires:</b> <code>x</code> refers to an object (if it |
| is a pointer type, it is non-null). <code>convertible() == |
| true</code>. |
| |
| <dt><b>Effects:</b> Creates an appropriately-typed Boost.Python |
| extension class instance, uses <code>MakeHolder</code> to create |
| an <code>instance_holder</code> from <code>x</code>, installs |
| the <code>instance_holder</code> in the new extension class |
| instance, and returns a pointer to it. |
| |
| </dl> |
| |
| |
| <h4><a name="to_python_indirect-spec-statics"></a>Class template <code>to_python_indirect</code> statics</h4> |
| <pre> |
| bool convertible(); |
| </pre> |
| |
| <dt><b>Effects:</b> Returns <code>true</code> iff any module has |
| registered a Python type corresponding to <code>U</code>. |
| |
| <h2><a name="examples"></a>Example</h2> |
| |
| This example replicates the functionality of <a |
| href="reference_existing_object.html#reference_existing_object-spec">reference_existing_object</a>, |
| but without some of the compile-time error checking. |
| |
| |
| <pre> |
| |
| struct make_reference_holder |
| { |
| typedef boost::python::objects::instance_holder* result_type; |
| template <class T> |
| static result_type execute(T* p) |
| { |
| return new boost::python::objects::pointer_holder<T*, T>(p); |
| } |
| }; |
| |
| struct reference_existing_object |
| { |
| // metafunction returning the <a href="ResultConverter.html#ResultConverter-concept">ResultConverter</a> |
| template <class T> |
| struct apply |
| { |
| typedef boost::python::to_python_indirect<T,make_reference_holder> type; |
| }; |
| }; |
| </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><i>© Copyright <a href="http://www.boost.org/people/dave_abrahams.htm">Dave |
| Abrahams</a> 2002. </i> 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)</p> |
| |