1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>boost/python/def_visitor.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_def_hpp.html" title="boost/python/def.hpp"> 10<link rel="next" href="boost_python_docstring_options_h.html" title="boost/python/docstring_options.hpp"> 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_def_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="boost_python_docstring_options_h.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_def_visitor_hpp"></a><a class="link" href="boost_python_def_visitor_hpp.html" title="boost/python/def_visitor.hpp">boost/python/def_visitor.hpp</a> 21</h2></div></div></div> 22<div class="toc"><dl class="toc"> 23<dt><span class="section"><a href="boost_python_def_visitor_hpp.html#high_level_components.boost_python_def_visitor_hpp.introduction">Introduction</a></span></dt> 24<dt><span class="section"><a href="boost_python_def_visitor_hpp.html#high_level_components.boost_python_def_visitor_hpp.class_def_visitor">Class 25 <code class="computeroutput"><span class="identifier">def_visitor</span></code></a></span></dt> 26<dt><span class="section"><a href="boost_python_def_visitor_hpp.html#high_level_components.boost_python_def_visitor_hpp.example">Example</a></span></dt> 27</dl></div> 28<div class="section"> 29<div class="titlepage"><div><div><h3 class="title"> 30<a name="high_level_components.boost_python_def_visitor_hpp.introduction"></a><a class="link" href="boost_python_def_visitor_hpp.html#high_level_components.boost_python_def_visitor_hpp.introduction" title="Introduction">Introduction</a> 31</h3></div></div></div> 32<p> 33 <boost/python/def_visitor.hpp> provides a generic visitation interface 34 through which the <a class="link" href="../high_level_components.html#high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel" title="Class template class_<T, Bases, HeldType, NonCopyable>">class_</a> 35 def member functionality can be extended non-intrusively to avoid cluttering 36 the <a class="link" href="../high_level_components.html#high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel" title="Class template class_<T, Bases, HeldType, NonCopyable>">class_</a> 37 interface. It declares the <code class="computeroutput"><span class="identifier">def_visitor</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> class template, which is parameterized 38 on the derived type <code class="computeroutput"><span class="identifier">DerivedVisitor</span></code>, 39 which provides the actual <code class="computeroutput"><span class="identifier">def</span></code> 40 functionality through its <code class="computeroutput"><span class="identifier">visit</span></code> 41 member functions. 42 </p> 43</div> 44<div class="section"> 45<div class="titlepage"><div><div><h3 class="title"> 46<a name="high_level_components.boost_python_def_visitor_hpp.class_def_visitor"></a><a class="link" href="boost_python_def_visitor_hpp.html#high_level_components.boost_python_def_visitor_hpp.class_def_visitor" title="Class def_visitor">Class 47 <code class="computeroutput"><span class="identifier">def_visitor</span></code></a> 48</h3></div></div></div> 49<p> 50 The class <code class="computeroutput"><span class="identifier">def_visitor</span></code> is 51 a base class paramaterized by its derived class. The <code class="computeroutput"><span class="identifier">def_visitor</span></code> 52 class is a protocol class. Its derived class, DerivedVisitor, is expected 53 to have a member function <code class="computeroutput"><span class="identifier">visit</span></code>. 54 The <code class="computeroutput"><span class="identifier">def_visitor</span></code> class is 55 never instantiated directly. Instead, an instance of its subclass, DerivedVisitor, 56 is passed on as an argument to the <a class="link" href="../high_level_components.html#high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel" title="Class template class_<T, Bases, HeldType, NonCopyable>">class_</a> 57 <code class="computeroutput"><span class="identifier">def</span></code> member function. 58 </p> 59<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">python</span> <span class="special">{</span> 60 61 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">DerivedVisitor</span><span class="special">></span> 62 <span class="keyword">class</span> <span class="identifier">def_visitor</span> <span class="special">{};</span> 63<span class="special">}</span> 64</pre> 65<div class="variablelist"> 66<p class="title"><b></b></p> 67<dl class="variablelist"> 68<dt><span class="term">Requires</span></dt> 69<dd> 70<p> 71 The client supplied class DerivedVisitor template parameter is expected 72 to: * be privately derived from def_visitor * grant friend access 73 to class def_visitor_access * define either or both visit member 74 functions listed in the table below: 75 </p> 76<div class="informaltable"><table class="table"> 77<colgroup> 78<col> 79<col> 80<col> 81<col> 82</colgroup> 83<thead><tr> 84<th> 85 <p> 86 Expression 87 </p> 88 </th> 89<th> 90 <p> 91 Return Type 92 </p> 93 </th> 94<th> 95 <p> 96 Requirements 97 </p> 98 </th> 99<th> 100 <p> 101 Effects 102 </p> 103 </th> 104</tr></thead> 105<tbody> 106<tr> 107<td> 108 <p> 109 <code class="computeroutput"><span class="identifier">visitor</span><span class="special">.</span><span class="identifier">visit</span><span class="special">(</span><span class="identifier">cls</span><span class="special">)</span></code> 110 </p> 111 </td> 112<td> 113 <p> 114 <code class="computeroutput"><span class="keyword">void</span></code> 115 </p> 116 </td> 117<td> 118 <p> 119 <code class="computeroutput"><span class="identifier">cls</span></code> is 120 an instance of a <a class="link" href="../high_level_components.html#high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel" title="Class template class_<T, Bases, HeldType, NonCopyable>">class_</a> 121 being wrapped to Python. <code class="computeroutput"><span class="identifier">visitor</span></code> 122 is a <code class="computeroutput"><span class="identifier">def_visitor</span></code> 123 derived class. 124 </p> 125 </td> 126<td> 127 <p> 128 A call to <code class="computeroutput"><span class="identifier">cls</span><span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="identifier">visitor</span><span class="special">)</span></code> forwards to this member 129 function. 130 </p> 131 </td> 132</tr> 133<tr> 134<td> 135 <p> 136 <code class="computeroutput"><span class="identifier">visitor</span><span class="special">.</span><span class="identifier">visit</span><span class="special">(</span><span class="identifier">cls</span><span class="special">,</span> <span class="identifier">name</span><span class="special">,</span> <span class="identifier">options</span><span class="special">)</span></code> 137 </p> 138 </td> 139<td> 140 <p> 141 <code class="computeroutput"><span class="keyword">void</span></code> 142 </p> 143 </td> 144<td> 145 <p> 146 <code class="computeroutput"><span class="identifier">cls</span></code> is 147 a <a class="link" href="../high_level_components.html#high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel" title="Class template class_<T, Bases, HeldType, NonCopyable>">class_</a> 148 instance, name is a C string. <code class="computeroutput"><span class="identifier">visitor</span></code> 149 is a <code class="computeroutput"><span class="identifier">def_visitor</span></code> 150 derived class. options is a context specific optional argument. 151 </p> 152 </td> 153<td> 154 <p> 155 A call to <code class="computeroutput"><span class="identifier">cls</span><span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="identifier">name</span><span class="special">,</span> <span class="identifier">visitor</span><span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">cls</span><span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="identifier">name</span><span class="special">,</span> <span class="identifier">visitor</span><span class="special">,</span> <span class="identifier">options</span><span class="special">)</span></code> forwards to this member 156 function. 157 </p> 158 </td> 159</tr> 160</tbody> 161</table></div> 162</dd> 163</dl> 164</div> 165</div> 166<div class="section"> 167<div class="titlepage"><div><div><h3 class="title"> 168<a name="high_level_components.boost_python_def_visitor_hpp.example"></a><a class="link" href="boost_python_def_visitor_hpp.html#high_level_components.boost_python_def_visitor_hpp.example" title="Example">Example</a> 169</h3></div></div></div> 170<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">X</span> <span class="special">{/*...*/};</span> 171 172<span class="keyword">class</span> <span class="identifier">my_def_visitor</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">def_visitor</span><span class="special"><</span><span class="identifier">my_def_visitor</span><span class="special">></span> 173<span class="special">{</span> 174 <span class="keyword">friend</span> <span class="keyword">class</span> <span class="identifier">def_visitor_access</span><span class="special">;</span> 175 176 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">classT</span><span class="special">></span> 177 <span class="keyword">void</span> <span class="identifier">visit</span><span class="special">(</span><span class="identifier">classT</span><span class="special">&</span> <span class="identifier">c</span><span class="special">)</span> <span class="keyword">const</span> 178 <span class="special">{</span> 179 <span class="identifier">c</span><span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="string">"foo"</span><span class="special">,</span> <span class="special">&</span><span class="identifier">my_def_visitor</span><span class="special">::</span><span class="identifier">foo</span><span class="special">);</span> 180 <span class="identifier">c</span><span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="string">"bar"</span><span class="special">,</span> <span class="special">&</span><span class="identifier">my_def_visitor</span><span class="special">::</span><span class="identifier">bar</span><span class="special">);</span> 181 <span class="special">}</span> 182 183 <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">foo</span><span class="special">(</span><span class="identifier">X</span><span class="special">&</span> <span class="identifier">self</span><span class="special">);</span> 184 <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">bar</span><span class="special">(</span><span class="identifier">X</span><span class="special">&</span> <span class="identifier">self</span><span class="special">);</span> 185<span class="special">};</span> 186 187<span class="identifier">BOOST_PYTHON_MODULE</span><span class="special">(</span><span class="identifier">my_ext</span><span class="special">)</span> 188<span class="special">{</span> 189 <span class="identifier">class_</span><span class="special"><</span><span class="identifier">X</span><span class="special">>(</span><span class="string">"X"</span><span class="special">)</span> 190 <span class="special">.</span><span class="identifier">def</span><span class="special">(</span><span class="identifier">my_def_visitor</span><span class="special">());</span> 191<span class="special">}</span> 192</pre> 193</div> 194</div> 195<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 196<td align="left"></td> 197<td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2015 David Abrahams, Stefan Seefeld<p> 198 Distributed under the Boost Software License, Version 1.0. (See accompanying 199 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> 200 </p> 201</div></td> 202</tr></table> 203<hr> 204<div class="spirit-nav"> 205<a accesskey="p" href="boost_python_def_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="boost_python_docstring_options_h.html"><img src="../../images/next.png" alt="Next"></a> 206</div> 207</body> 208</html> 209
