1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>boost/python/wrapper.hpp</title> 5<link rel="stylesheet" href="../../boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../index.html" title="Boost.Python Reference Manual"> 8<link rel="up" href="../high_level_components.html" title="Chapter 2. High Level Components"> 9<link rel="prev" href="boost_python_stl_iterator_hpp.html" title="boost/python/stl_iterator.hpp"> 10<link rel="next" href="../object_wrappers.html" title="Chapter 3. Object Wrappers"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="" width="" height="" src="../../images/boost.png"></td></tr></table> 14<hr> 15<div class="spirit-nav"> 16<a accesskey="p" href="boost_python_stl_iterator_hpp.html"><img src="../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../high_level_components.html"><img src="../../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../images/home.png" alt="Home"></a><a accesskey="n" href="../object_wrappers.html"><img src="../../images/next.png" alt="Next"></a> 17</div> 18<div class="section"> 19<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 20<a name="high_level_components.boost_python_wrapper_hpp"></a><a class="link" href="boost_python_wrapper_hpp.html" title="boost/python/wrapper.hpp">boost/python/wrapper.hpp</a> 21</h2></div></div></div> 22<div class="toc"><dl class="toc"> 23<dt><span class="section"><a href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.introduction">Introduction</a></span></dt> 24<dt><span class="section"><a href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_override">Class 25 <code class="computeroutput"><span class="identifier">override</span></code></a></span></dt> 26<dt><span class="section"><a href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_override_observer_function">Class 27 <code class="computeroutput"><span class="identifier">override</span></code> observer functions</a></span></dt> 28<dt><span class="section"><a href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_template_wrapper">Class 29 template <code class="computeroutput"><span class="identifier">wrapper</span></code></a></span></dt> 30<dt><span class="section"><a href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_template_wrapper_observer_">Class 31 template <code class="computeroutput"><span class="identifier">wrapper</span></code> observer 32 functions</a></span></dt> 33<dt><span class="section"><a href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.example">Example</a></span></dt> 34</dl></div> 35<div class="section"> 36<div class="titlepage"><div><div><h3 class="title"> 37<a name="high_level_components.boost_python_wrapper_hpp.introduction"></a><a class="link" href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.introduction" title="Introduction">Introduction</a> 38</h3></div></div></div> 39<p> 40 To wrap a class T such that its virtual functions can be "overridden 41 in Python"—so that the corresponding method of a Python derived 42 class will be called when the virtual function is invoked from C++—you 43 must create a C++ wrapper class derived from <code class="computeroutput"><span class="identifier">T</span></code> 44 that overrides those virtual functions so that they call into Python. This 45 header contains classes that can be used to make that job easier. 46 </p> 47</div> 48<div class="section"> 49<div class="titlepage"><div><div><h3 class="title"> 50<a name="high_level_components.boost_python_wrapper_hpp.class_override"></a><a class="link" href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_override" title="Class override">Class 51 <code class="computeroutput"><span class="identifier">override</span></code></a> 52</h3></div></div></div> 53<p> 54 Encapsulates a Python override of a C++ virtual function. An override object 55 either holds a callable Python object or <code class="computeroutput"><span class="identifier">None</span></code>. 56 </p> 57<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> 58<span class="special">{</span> 59 <span class="keyword">class</span> <span class="identifier">override</span> <span class="special">:</span> <span class="identifier">object</span> 60 <span class="special">{</span> 61 <span class="keyword">public</span><span class="special">:</span> 62 <span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 63 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">></span> 64 <span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">(</span><span class="identifier">A0</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 65 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">A1</span><span class="special">></span> 66 <span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">(</span><span class="identifier">A0</span><span class="special">,</span> <span class="identifier">A1</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 67 <span class="special">...</span> 68 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">A1</span><span class="special">,</span> <span class="special">...</span><span class="keyword">class</span> <span class="identifier">An</span><span class="special">></span> 69 <span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">(</span><span class="identifier">A0</span><span class="special">,</span> <span class="identifier">A1</span><span class="special">,</span> <span class="special">...</span><span class="identifier">An</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 70 <span class="special">};</span> 71<span class="special">};</span> 72</pre> 73</div> 74<div class="section"> 75<div class="titlepage"><div><div><h3 class="title"> 76<a name="high_level_components.boost_python_wrapper_hpp.class_override_observer_function"></a><a class="link" href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_override_observer_function" title="Class override observer functions">Class 77 <code class="computeroutput"><span class="identifier">override</span></code> observer functions</a> 78</h3></div></div></div> 79<pre class="programlisting"><span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 80<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">></span> 81<span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">(</span><span class="identifier">A0</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 82<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">A1</span><span class="special">></span> 83<span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">(</span><span class="identifier">A0</span><span class="special">,</span> <span class="identifier">A1</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 84<span class="special">...</span> 85<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">A0</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">A1</span><span class="special">,</span> <span class="special">...</span><span class="keyword">class</span> <span class="identifier">An</span><span class="special">></span> 86<span class="identifier">unspecified</span> <span class="keyword">operator</span><span class="special">(</span><span class="identifier">A0</span><span class="special">,</span> <span class="identifier">A1</span><span class="special">,</span> <span class="special">...</span><span class="identifier">An</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 87</pre> 88<div class="variablelist"> 89<p class="title"><b></b></p> 90<dl class="variablelist"> 91<dt><span class="term">Effects</span></dt> 92<dd><p> 93 If *this holds a callable Python object, it is invoked with the specified 94 arguments in the manner specified here. Otherwise, throws <a class="link" href="boost_python_errors_hpp.html#high_level_components.boost_python_errors_hpp.class_error_already_set" title="Class error_already_set">error_already_set</a>. 95 </p></dd> 96<dt><span class="term">Returns</span></dt> 97<dd><p> 98 An object of unspecified type that holds the Python result of the 99 invocation and, when converted to a C++ type R, attempts to convert 100 that result object to R. If that conversion fails, throws <a class="link" href="boost_python_errors_hpp.html#high_level_components.boost_python_errors_hpp.class_error_already_set" title="Class error_already_set">error_already_set</a>. 101 </p></dd> 102</dl> 103</div> 104</div> 105<div class="section"> 106<div class="titlepage"><div><div><h3 class="title"> 107<a name="high_level_components.boost_python_wrapper_hpp.class_template_wrapper"></a><a class="link" href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_template_wrapper" title="Class template wrapper">Class 108 template <code class="computeroutput"><span class="identifier">wrapper</span></code></a> 109</h3></div></div></div> 110<p> 111 Deriving your wrapper class from both <code class="computeroutput"><span class="identifier">T</span></code> 112 and <code class="computeroutput"><span class="identifier">wrapper</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> 113 makes writing that derived class easier. 114 </p> 115<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> 116<span class="special">{</span> 117 <span class="keyword">class</span> <span class="identifier">wrapper</span> 118 <span class="special">{</span> 119 <span class="keyword">protected</span><span class="special">:</span> 120 <span class="identifier">override</span> <span class="identifier">get_override</span><span class="special">(</span><span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">name</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 121 <span class="special">};</span> 122<span class="special">};</span> 123</pre> 124</div> 125<div class="section"> 126<div class="titlepage"><div><div><h3 class="title"> 127<a name="high_level_components.boost_python_wrapper_hpp.class_template_wrapper_observer_"></a><a class="link" href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.class_template_wrapper_observer_" title="Class template wrapper observer functions">Class 128 template <code class="computeroutput"><span class="identifier">wrapper</span></code> observer 129 functions</a> 130</h3></div></div></div> 131<pre class="programlisting"><span class="identifier">override</span> <span class="identifier">get_override</span><span class="special">(</span><span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">name</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> 132<div class="variablelist"> 133<p class="title"><b></b></p> 134<dl class="variablelist"> 135<dt><span class="term">Requires</span></dt> 136<dd><p> 137 name is a <a class="link" href="../glossary.html#ntbs">ntbs</a>. 138 </p></dd> 139<dt><span class="term">Returns</span></dt> 140<dd><p> 141 If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> 142 is the C++ base class subobject of a Python derived class instance 143 that overrides the named function, returns an override object that 144 delegates to the Python override. Otherwise, returns an override 145 object that holds <code class="computeroutput"><span class="identifier">None</span></code>. 146 </p></dd> 147</dl> 148</div> 149</div> 150<div class="section"> 151<div class="titlepage"><div><div><h3 class="title"> 152<a name="high_level_components.boost_python_wrapper_hpp.example"></a><a class="link" href="boost_python_wrapper_hpp.html#high_level_components.boost_python_wrapper_hpp.example" title="Example">Example</a> 153</h3></div></div></div> 154<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">python</span><span class="special">/</span><span class="identifier">module</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 155<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">python</span><span class="special">/</span><span class="keyword">class</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 156<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">python</span><span class="special">/</span><span class="identifier">wrapper</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 157<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">python</span><span class="special">/</span><span class="identifier">call</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 158 159<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">python</span><span class="special">;</span> 160 161<span class="comment">// Class with one pure virtual function</span> 162<span class="keyword">struct</span> <span class="identifier">P</span> 163<span class="special">{</span> 164 <span class="keyword">virtual</span> <span class="special">~</span><span class="identifier">P</span><span class="special">(){}</span> 165 <span class="keyword">virtual</span> <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">f</span><span class="special">()</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> 166 <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">g</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="string">"P::g()"</span><span class="special">;</span> <span class="special">}</span> 167<span class="special">};</span> 168 169<span class="keyword">struct</span> <span class="identifier">PCallback</span> <span class="special">:</span> <span class="identifier">P</span><span class="special">,</span> <span class="identifier">wrapper</span><span class="special"><</span><span class="identifier">P</span><span class="special">></span> 170<span class="special">{</span> 171 <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">f</span><span class="special">()</span> 172 <span class="special">{</span> 173 <span class="keyword">return</span> <span class="keyword">this</span><span class="special">-></span><span class="identifier">get_override</span><span class="special">(</span><span class="string">"f"</span><span class="special">)();</span> 174 <span class="special">}</span> 175<span class="special">};</span> 176 177<span class="comment">// Class with one non-pure virtual function</span> 178<span class="keyword">struct</span> <span class="identifier">A</span> 179<span class="special">{</span> 180 <span class="keyword">virtual</span> <span class="special">~</span><span class="identifier">A</span><span class="special">(){}</span> 181 <span class="keyword">virtual</span> <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">f</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="string">"A::f()"</span><span class="special">;</span> <span class="special">}</span> 182<span class="special">};</span> 183 184<span class="keyword">struct</span> <span class="identifier">ACallback</span> <span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">wrapper</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> 185<span class="special">{</span> 186 <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">f</span><span class="special">()</span> 187 <span class="special">{</span> 188 <span class="keyword">if</span> <span class="special">(</span><span class="identifier">override</span> <span class="identifier">f</span> <span class="special">=</span> <span class="keyword">this</span><span class="special">-></span><span class="identifier">get_override</span><span class="special">(</span><span class="string">"f"</span><span class="special">))</span> 189 <span class="keyword">return</span> <span class="identifier">f</span><span class="special">();</span> 190 <span class="keyword">return</span> <span class="identifier">A</span><span class="special">::</span><span class="identifier">f</span><span class="special">();</span> 191 <span class="special">}</span> 192 193 <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">default_f</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="keyword">this</span><span class="special">-></span><span class="identifier">A</span><span class="special">::</span><span class="identifier">f</span><span class="special">();</span> <span class="special">}</span> 194<span class="special">};</span> 195 196<span class="identifier">BOOST_PYTHON_MODULE_INIT</span><span class="special">(</span><span class="identifier">polymorphism</span><span class="special">)</span> 197<span class="special">{</span> 198 <span class="identifier">class_</span><span class="special"><</span><span class="identifier">PCallback</span><span class="special">,</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">noncopyable</span><span class="special">>(</span><span class="string">"P"</span><span class="special">)</span> 199 <span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="string">"f"</span><span class="special">,</span> <span class="identifier">pure_virtual</span><span class="special">(&</span><span class="identifier">P</span><span class="special">::</span><span class="identifier">f</span><span class="special">))</span> 200 <span class="special">;</span> 201 202 <span class="identifier">class_</span><span class="special"><</span><span class="identifier">ACallback</span><span class="special">,</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">noncopyable</span><span class="special">>(</span><span class="string">"A"</span><span class="special">)</span> 203 <span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="string">"f"</span><span class="special">,</span> <span class="special">&</span><span class="identifier">A</span><span class="special">::</span><span class="identifier">f</span><span class="special">,</span> <span class="special">&</span><span class="identifier">ACallback</span><span class="special">::</span><span class="identifier">default_f</span><span class="special">)</span> 204 <span class="special">;</span> 205<span class="special">}</span> 206</pre> 207</div> 208</div> 209<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 210<td align="left"></td> 211<td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2015 David Abrahams, Stefan Seefeld<p> 212 Distributed under the Boost Software License, Version 1.0. (See accompanying 213 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a> 214 </p> 215</div></td> 216</tr></table> 217<hr> 218<div class="spirit-nav"> 219<a accesskey="p" href="boost_python_stl_iterator_hpp.html"><img src="../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../high_level_components.html"><img src="../../images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../images/home.png" alt="Home"></a><a accesskey="n" href="../object_wrappers.html"><img src="../../images/next.png" alt="Next"></a> 220</div> 221</body> 222</html> 223
