195 lines
6.1 KiB
HTML
195 lines
6.1 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<meta name="generator" content="HTML Tidy, see www.w3.org">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link rel="stylesheet" type="text/css" href="../boost.css">
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<title>Boost.Python - <boost/python/to_python_indirect.hpp></title>
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<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
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"header">
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<tr>
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<td valign="top" width="300">
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<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
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"C++ Boost" src="../../../../boost.png" border="0"></a></h3>
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<td valign="top">
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<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
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<h2 align="center">Header <boost/python/to_python_indirect.hpp></h2>
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</table>
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<hr>
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<h2>Contents</h2>
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<dl class="page-index">
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<dt><a href="#introduction">Introduction</a>
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<dt><a href="#classes">Classes</a>
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<dd>
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<dl class="page-index">
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<dt><a href="#to_python_indirect-spec">Class Template <code>to_python_indirect</code></a>
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<dd>
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<dl class="page-index">
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<dt><a href="#to_python_indirect-spec-synopsis">Class Template
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<code>to_python_indirect</code> synopsis</a>
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<dt><a href="#to_python_indirect-spec-observers">Class Template
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<code>to_python_indirect</code> observer functions</a>
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<dt><a href="#to_python_indirect-spec-statics">Class Template
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<code>to_python_indirect</code> static functions</a>
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</dl>
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</dl>
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<dt><a href="#examples">Example</a>
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</dl>
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<hr>
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<h2><a name="introduction"></a>Introduction</h2>
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<code><boost/python/to_python_indirect.hpp></code> supplies
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a way to construct new Python objects that hold wrapped C++ class
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instances via a pointer or smart pointer.
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<h2><a name="classes"></a>Classes</h2>
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<h3><a name="to_python_indirect-spec"></a>Class template <code>to_python_indirect</code></h3>
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<p>Class template <code>to_python_indirect</code> converts objects
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of its first argument type to python as extension class instances, using the ownership policy provided by its 2nd argument.
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<p>
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<table border="1" summary="to_python_indirect template parameters">
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<caption>
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<b><code>to_python_indirect</code> Requirements</b><br>
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In the table below, <b><code>x</code></b> denotes an object of
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type <code>T</code>, <b><code>h</code></b> denotes an
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object of type
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<code>boost::python::objects::instance_holder*</code>, and
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<b><code>p</code></b> denotes an object of type
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<code>U*</code>.
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</caption>
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<tr>
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<th>Parameter
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<th>Requirements
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<th>Description
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<tr>
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<td><code>T</code>
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<td>Either <code>U</code> <i>cv</i><code>&</code>
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(where <i>cv</i> is any optional cv-qualification) or a <a
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href="Dereferenceable.html">Dereferenceable</a> type such that
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<code>*x</code> is convertible to <code>U const&</code>, where
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<code>U</code> is a class type.
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<td>A type deferencing a C++ class exposed to Python using
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class template <code><a
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href="class.html#class_-spec">class_</a></code>.
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<tr>
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<td><code>MakeHolder</code>
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<td>h = MakeHolder::execute(p);
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<td>A class whose static <code>execute()</code> creates an
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<code>instance_holder</code>.
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</table>
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Instantiations of <code>to_python_indirect</code> are models of <a
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href="ResultConverter.html#ResultConverter-concept">ResultConverter</a>.
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<h4><a name="to_python_indirect-spec-synopsis"></a>Class template <code>to_python_indirect</code> synopsis</h4>
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<pre>
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namespace boost { namespace python
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{
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template <class T, class MakeHolder>
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struct to_python_indirect
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{
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static bool convertible();
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PyObject* operator()(T ptr_or_reference) const;
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private:
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static PyTypeObject* type();
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};
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}}
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</pre>
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<h4><a name="to_python_indirect-spec-observers"></a>Class template <code>to_python_indirect</code> observers</h4>
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<pre>
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PyObject* operator()(T x) const;
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> <code>x</code> refers to an object (if it
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is a pointer type, it is non-null). <code>convertible() ==
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true</code>.
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<dt><b>Effects:</b> Creates an appropriately-typed Boost.Python
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extension class instance, uses <code>MakeHolder</code> to create
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an <code>instance_holder</code> from <code>x</code>, installs
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the <code>instance_holder</code> in the new extension class
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instance, and returns a pointer to it.
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</dl>
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<h4><a name="to_python_indirect-spec-statics"></a>Class template <code>to_python_indirect</code> statics</h4>
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<pre>
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bool convertible();
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</pre>
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<dt><b>Effects:</b> Returns <code>true</code> iff any module has
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registered a Python type corresponding to <code>U</code>.
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<h2><a name="examples"></a>Example</h2>
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This example replicates the functionality of <a
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href="reference_existing_object.html#reference_existing_object-spec">reference_existing_object</a>,
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but without some of the compile-time error checking.
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<pre>
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struct make_reference_holder
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{
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typedef boost::python::objects::instance_holder* result_type;
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template <class T>
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static result_type execute(T* p)
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{
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return new boost::python::objects::pointer_holder<T*, T>(p);
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}
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};
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struct reference_existing_object
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{
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// metafunction returning the <a href="ResultConverter.html#ResultConverter-concept">ResultConverter</a>
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template <class T>
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struct apply
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{
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typedef boost::python::to_python_indirect<T,make_reference_holder> type;
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};
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};
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</pre>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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13 November, 2002
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<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
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Abrahams</a> 2002. All Rights Reserved.</i>
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