1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>boost/python/handle.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="../utility_and_infrastructure.html" title="Chapter 7. Utility and Infrastructure"> 9<link rel="prev" href="boost_python_pointee_hpp.html" title="boost/python/pointee.hpp"> 10<link rel="next" href="boost_python_type_id_hpp.html" title="boost/python/type_id.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_pointee_hpp.html"><img src="../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../utility_and_infrastructure.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_type_id_hpp.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="utility_and_infrastructure.boost_python_handle_hpp"></a><a class="link" href="boost_python_handle_hpp.html" title="boost/python/handle.hpp">boost/python/handle.hpp</a> 21</h2></div></div></div> 22<div class="toc"><dl class="toc"> 23<dt><span class="section"><a href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.introduction">Introduction</a></span></dt> 24<dt><span class="section"><a href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle">Class 25 template <code class="computeroutput"><span class="identifier">handle</span></code></a></span></dt> 26<dt><span class="section"><a href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.function_borrowed">Function 27 <code class="computeroutput"><span class="identifier">borrowed</span></code></a></span></dt> 28<dt><span class="section"><a href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.function_allow_null">Function 29 <code class="computeroutput"><span class="identifier">allow_null</span></code></a></span></dt> 30</dl></div> 31<div class="section"> 32<div class="titlepage"><div><div><h3 class="title"> 33<a name="utility_and_infrastructure.boost_python_handle_hpp.introduction"></a><a class="link" href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.introduction" title="Introduction">Introduction</a> 34</h3></div></div></div> 35<p> 36 <boost/python/handle.hpp> provides class template <code class="computeroutput"><span class="identifier">handle</span></code>, 37 a smart pointer for managing reference-counted Python objects. 38 </p> 39</div> 40<div class="section"> 41<div class="titlepage"><div><div><h3 class="title"> 42<a name="utility_and_infrastructure.boost_python_handle_hpp.class_template_handle"></a><a class="link" href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle" title="Class template handle">Class 43 template <code class="computeroutput"><span class="identifier">handle</span></code></a> 44</h3></div></div></div> 45<div class="toc"><dl class="toc"> 46<dt><span class="section"><a href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_constructo">Class 47 template <code class="computeroutput"><span class="identifier">handle</span></code> constructors 48 and destructor</a></span></dt> 49<dt><span class="section"><a href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_modifiers">Class 50 template <code class="computeroutput"><span class="identifier">handle</span></code> modifiers</a></span></dt> 51<dt><span class="section"><a href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_observers">Class 52 template <code class="computeroutput"><span class="identifier">handle</span></code> observers</a></span></dt> 53</dl></div> 54<p> 55 <code class="computeroutput"><span class="identifier">handle</span></code> is a smart pointer 56 to a Python object type; it holds a pointer of type <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span></code>, where <code class="computeroutput"><span class="identifier">T</span></code> 57 is its template parameter. T must be either a type derived from <code class="computeroutput"><span class="identifier">PyObject</span></code> or a <a class="link" href="../glossary.html#pod">POD</a> 58 type whose initial <code class="computeroutput"><span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">PyObject</span><span class="special">)</span></code> bytes are layout-compatible with <code class="computeroutput"><span class="identifier">PyObject</span></code>. Use <code class="computeroutput"><span class="identifier">handle</span><span class="special"><></span></code> at the boundary between the Python/'C' 59 API and high-level code; prefer object for a generalized interface to Python 60 objects. 61 </p> 62<p> 63 In this document, the term "upcast" refers to an operation which 64 converts a pointer <code class="computeroutput"><span class="identifier">Y</span><span class="special">*</span></code> 65 to a base class <code class="computeroutput"><span class="identifier">pointer</span> <span class="identifier">T</span><span class="special">*</span></code> via 66 <code class="computeroutput"><span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">T</span><span class="special">*></span></code> 67 if <code class="computeroutput"><span class="identifier">Y</span></code> is derived from <code class="computeroutput"><span class="identifier">T</span></code>, or via C-style cast (<code class="computeroutput"><span class="identifier">T</span><span class="special">*</span></code>) if 68 it is not. However, in the latter case the "upcast" is ill-formed 69 if the initial <code class="computeroutput"><span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">PyObject</span><span class="special">)</span></code> 70 bytes of <code class="computeroutput"><span class="identifier">Y</span></code> are not layout-compatible 71 with <code class="computeroutput"><span class="identifier">PyObject</span></code>. 72 </p> 73<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> 74<span class="special">{</span> 75 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> 76 <span class="keyword">class</span> <span class="identifier">handle</span> 77 <span class="special">{</span> 78 <span class="keyword">typedef</span> <span class="identifier">unspecified</span><span class="special">-</span><span class="identifier">member</span><span class="special">-</span><span class="identifier">function</span><span class="special">-</span><span class="identifier">pointer</span> <span class="identifier">bool_type</span><span class="special">;</span> 79 80 <span class="keyword">public</span><span class="special">:</span> <span class="comment">// types</span> 81 <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="identifier">element_type</span><span class="special">;</span> 82 83 <span class="keyword">public</span><span class="special">:</span> <span class="comment">// member functions</span> 84 <span class="special">~</span><span class="identifier">handle</span><span class="special">();</span> 85 86 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 87 <span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span> 88 89 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 90 <span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span> 91 92 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 93 <span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span> 94 95 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 96 <span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span> 97 98 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 99 <span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">Y</span><span class="special">*</span> <span class="identifier">p</span><span class="special">);</span> 100 101 <span class="identifier">handle</span><span class="special">();</span> 102 103 <span class="identifier">handle</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="identifier">handle</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> 104 105 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Y</span><span class="special">></span> 106 <span class="identifier">handle</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="identifier">handle</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="keyword">const</span> <span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> <span class="comment">// never throws</span> 107 108 109 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Y</span><span class="special">></span> 110 <span class="identifier">handle</span><span class="special">(</span><span class="identifier">handle</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> 111 112 <span class="identifier">handle</span><span class="special">(</span><span class="identifier">handle</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> 113 114 <span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span><span class="special">-></span> <span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 115 <span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*</span> <span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 116 <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 117 <span class="keyword">void</span> <span class="identifier">reset</span><span class="special">();</span> 118 <span class="identifier">T</span><span class="special">*</span> <span class="identifier">release</span><span class="special">();</span> 119 120 <span class="keyword">operator</span> <span class="identifier">bool_type</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> <span class="comment">// never throws</span> 121 <span class="keyword">private</span><span class="special">:</span> 122 <span class="identifier">T</span><span class="special">*</span> <span class="identifier">m_p</span><span class="special">;</span> 123 <span class="special">};</span> 124 125 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">null_ok</span><span class="special">;</span> 126 <span class="keyword">namespace</span> <span class="identifier">detail</span> <span class="special">{</span> <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">borrowed</span><span class="special">;</span> <span class="special">}</span> 127<span class="special">}}</span> 128</pre> 129<div class="section"> 130<div class="titlepage"><div><div><h4 class="title"> 131<a name="utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_constructo"></a><a class="link" href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_constructo" title="Class template handle constructors and destructor">Class 132 template <code class="computeroutput"><span class="identifier">handle</span></code> constructors 133 and destructor</a> 134</h4></div></div></div> 135<pre class="programlisting"><span class="keyword">virtual</span> <span class="special">~</span><span class="identifier">handle</span><span class="special">();</span></pre> 136<div class="variablelist"> 137<p class="title"><b></b></p> 138<dl class="variablelist"> 139<dt><span class="term">Effects</span></dt> 140<dd><p> 141 <code class="computeroutput"><span class="identifier">Py_XDECREF</span><span class="special">(</span><span class="identifier">upcast</span><span class="special"><</span><span class="identifier">PyObject</span><span class="special">*>(</span><span class="identifier">m_p</span><span class="special">))</span></code> 142 </p></dd> 143</dl> 144</div> 145<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 146<span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span> 147</pre> 148<div class="variablelist"> 149<p class="title"><b></b></p> 150<dl class="variablelist"> 151<dt><span class="term">Effects</span></dt> 152<dd><pre class="programlisting"><span class="identifier">Py_XINCREF</span><span class="special">(</span><span class="identifier">upcast</span><span class="special"><</span><span class="identifier">PyObject</span><span class="special">*>(</span><span class="identifier">p</span><span class="special">));</span> 153<span class="identifier">m_p</span> <span class="special">=</span> <span class="identifier">upcast</span><span class="special"><</span><span class="identifier">T</span><span class="special">*>(</span><span class="identifier">p</span><span class="special">);</span> 154</pre></dd> 155</dl> 156</div> 157<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 158<span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span></pre> 159<div class="variablelist"> 160<p class="title"><b></b></p> 161<dl class="variablelist"> 162<dt><span class="term">Effects</span></dt> 163<dd><pre class="programlisting"><span class="identifier">Py_XINCREF</span><span class="special">(</span><span class="identifier">upcast</span><span class="special"><</span><span class="identifier">PyObject</span><span class="special">*>(</span><span class="identifier">p</span><span class="special">));</span> 164 <span class="identifier">m_p</span> <span class="special">=</span> <span class="identifier">upcast</span><span class="special"><</span><span class="identifier">T</span><span class="special">*>(</span><span class="identifier">p</span><span class="special">);</span> 165</pre></dd> 166</dl> 167</div> 168<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 169<span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span></pre> 170<div class="variablelist"> 171<p class="title"><b></b></p> 172<dl class="variablelist"> 173<dt><span class="term">Effects</span></dt> 174<dd><pre class="programlisting"><span class="identifier">Py_XINCREF</span><span class="special">(</span><span class="identifier">upcast</span><span class="special"><</span><span class="identifier">PyObject</span><span class="special">*>(</span><span class="identifier">p</span><span class="special">));</span> 175 <span class="identifier">m_p</span> <span class="special">=</span> <span class="identifier">upcast</span><span class="special"><</span><span class="identifier">T</span><span class="special">*>(</span><span class="identifier">expect_non_null</span><span class="special">(</span><span class="identifier">p</span><span class="special">));</span> 176</pre></dd> 177</dl> 178</div> 179<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 180<span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">Y</span><span class="special">>*</span> <span class="identifier">p</span><span class="special">);</span> 181</pre> 182<div class="variablelist"> 183<p class="title"><b></b></p> 184<dl class="variablelist"> 185<dt><span class="term">Effects</span></dt> 186<dd><p> 187 <code class="computeroutput"><span class="identifier">m_p</span> <span class="special">=</span> 188 <span class="identifier">upcast</span><span class="special"><</span><span class="identifier">T</span><span class="special">*>(</span><span class="identifier">p</span><span class="special">);</span></code> 189 </p></dd> 190</dl> 191</div> 192<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Y</span><span class="special">></span> 193<span class="keyword">explicit</span> <span class="identifier">handle</span><span class="special">(</span><span class="identifier">Y</span><span class="special">*</span> <span class="identifier">p</span><span class="special">);</span> 194</pre> 195<div class="variablelist"> 196<p class="title"><b></b></p> 197<dl class="variablelist"> 198<dt><span class="term">Effects</span></dt> 199<dd><p> 200 <code class="computeroutput"><span class="identifier">m_p</span> <span class="special">=</span> 201 <span class="identifier">upcast</span><span class="special"><</span><span class="identifier">T</span><span class="special">*>(</span><span class="identifier">expect_non_null</span><span class="special">(</span><span class="identifier">p</span><span class="special">));</span></code> 202 </p></dd> 203</dl> 204</div> 205<pre class="programlisting"><span class="identifier">handle</span><span class="special">();</span> 206</pre> 207<div class="variablelist"> 208<p class="title"><b></b></p> 209<dl class="variablelist"> 210<dt><span class="term">Effects</span></dt> 211<dd><p> 212 <code class="computeroutput"><span class="identifier">m_p</span> <span class="special">=</span> 213 <span class="number">0</span><span class="special">;</span></code> 214 </p></dd> 215</dl> 216</div> 217<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Y</span><span class="special">></span> 218<span class="identifier">handle</span><span class="special">(</span><span class="identifier">handle</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> 219<span class="identifier">handle</span><span class="special">(</span><span class="identifier">handle</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> 220</pre> 221<div class="variablelist"> 222<p class="title"><b></b></p> 223<dl class="variablelist"> 224<dt><span class="term">Effects</span></dt> 225<dd><p> 226 m_p = r.m_p; Py_XINCREF(upcast<PyObject*>(m_p)); 227 </p></dd> 228</dl> 229</div> 230</div> 231<div class="section"> 232<div class="titlepage"><div><div><h4 class="title"> 233<a name="utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_modifiers"></a><a class="link" href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_modifiers" title="Class template handle modifiers">Class 234 template <code class="computeroutput"><span class="identifier">handle</span></code> modifiers</a> 235</h4></div></div></div> 236<pre class="programlisting"><span class="identifier">handle</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="identifier">handle</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> 237<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Y</span><span class="special">></span> 238<span class="identifier">handle</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">=(</span><span class="identifier">handle</span><span class="special"><</span><span class="identifier">Y</span><span class="special">></span> <span class="keyword">const</span> <span class="special">&</span> <span class="identifier">r</span><span class="special">);</span> <span class="comment">// never throws</span> 239</pre> 240<div class="variablelist"> 241<p class="title"><b></b></p> 242<dl class="variablelist"> 243<dt><span class="term">Effects</span></dt> 244<dd><p> 245 <code class="computeroutput"><span class="identifier">Py_XINCREF</span><span class="special">(</span><span class="identifier">upcast</span><span class="special"><</span><span class="identifier">PyObject</span><span class="special">*>(</span><span class="identifier">r</span><span class="special">.</span><span class="identifier">m_p</span><span class="special">));</span> 246 <span class="identifier">Py_XDECREF</span><span class="special">(</span> 247 <span class="identifier">upcast</span><span class="special"><</span><span class="identifier">PyObject</span><span class="special">*>(</span><span class="identifier">m_p</span><span class="special">));</span> 248 <span class="identifier">m_p</span> <span class="special">=</span> 249 <span class="identifier">r</span><span class="special">.</span><span class="identifier">m_p</span><span class="special">;</span></code> 250 </p></dd> 251</dl> 252</div> 253<pre class="programlisting"><span class="identifier">T</span><span class="special">*</span> <span class="identifier">release</span><span class="special">();</span> 254</pre> 255<div class="variablelist"> 256<p class="title"><b></b></p> 257<dl class="variablelist"> 258<dt><span class="term">Effects</span></dt> 259<dd><p> 260 <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> 261 <span class="identifier">x</span> <span class="special">=</span> 262 <span class="identifier">m_p</span><span class="special">;</span> 263 <span class="identifier">m_p</span> <span class="special">=</span> 264 <span class="number">0</span><span class="special">;</span> 265 <span class="keyword">return</span> <span class="identifier">x</span><span class="special">;</span></code> 266 </p></dd> 267</dl> 268</div> 269<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">reset</span><span class="special">();</span> 270</pre> 271<div class="variablelist"> 272<p class="title"><b></b></p> 273<dl class="variablelist"> 274<dt><span class="term">Effects</span></dt> 275<dd><p> 276 <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> 277 <span class="special">=</span> <span class="identifier">handle</span><span class="special"><</span><span class="identifier">T</span><span class="special">>();</span></code> 278 </p></dd> 279</dl> 280</div> 281</div> 282<div class="section"> 283<div class="titlepage"><div><div><h4 class="title"> 284<a name="utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_observers"></a><a class="link" href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.class_template_handle.class_template_handle_observers" title="Class template handle observers">Class 285 template <code class="computeroutput"><span class="identifier">handle</span></code> observers</a> 286</h4></div></div></div> 287<pre class="programlisting"><span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span><span class="special">-></span> <span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 288<span class="identifier">T</span><span class="special">*</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 289</pre> 290<div class="variablelist"> 291<p class="title"><b></b></p> 292<dl class="variablelist"> 293<dt><span class="term">Returns</span></dt> 294<dd><p> 295 <code class="computeroutput"><span class="identifier">m_p</span><span class="special">;</span></code> 296 </p></dd> 297</dl> 298</div> 299<pre class="programlisting"><span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*</span> <span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> 300</pre> 301<div class="variablelist"> 302<p class="title"><b></b></p> 303<dl class="variablelist"> 304<dt><span class="term">Returns</span></dt> 305<dd><p> 306 <code class="computeroutput"><span class="special">*</span><span class="identifier">m_p</span><span class="special">;</span></code> 307 </p></dd> 308</dl> 309</div> 310<pre class="programlisting"><span class="keyword">operator</span> <span class="identifier">bool_type</span><span class="special">()</span> <span class="keyword">const</span><span class="special">;</span> <span class="comment">// never throws</span> 311</pre> 312<div class="variablelist"> 313<p class="title"><b></b></p> 314<dl class="variablelist"> 315<dt><span class="term">Returns</span></dt> 316<dd><p> 317 <code class="computeroutput"><span class="number">0</span></code> if <code class="computeroutput"><span class="identifier">m_p</span> <span class="special">==</span> 318 <span class="number">0</span></code>, a pointer convertible 319 to true otherwise. 320 </p></dd> 321</dl> 322</div> 323</div> 324</div> 325<div class="section"> 326<div class="titlepage"><div><div><h3 class="title"> 327<a name="utility_and_infrastructure.boost_python_handle_hpp.function_borrowed"></a><a class="link" href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.function_borrowed" title="Function borrowed">Function 328 <code class="computeroutput"><span class="identifier">borrowed</span></code></a> 329</h3></div></div></div> 330<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> 331<span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">T</span><span class="special">>*</span> <span class="identifier">borrowed</span><span class="special">(</span><span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span><span class="special">)</span> 332<span class="special">{</span> 333 <span class="keyword">return</span> <span class="special">(</span><span class="identifier">detail</span><span class="special">::</span><span class="identifier">borrowed</span><span class="special"><</span><span class="identifier">T</span><span class="special">>*)</span><span class="identifier">p</span><span class="special">;</span> 334<span class="special">}</span> 335</pre> 336</div> 337<div class="section"> 338<div class="titlepage"><div><div><h3 class="title"> 339<a name="utility_and_infrastructure.boost_python_handle_hpp.function_allow_null"></a><a class="link" href="boost_python_handle_hpp.html#utility_and_infrastructure.boost_python_handle_hpp.function_allow_null" title="Function allow_null">Function 340 <code class="computeroutput"><span class="identifier">allow_null</span></code></a> 341</h3></div></div></div> 342<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> 343<span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">T</span><span class="special">>*</span> <span class="identifier">allow_null</span><span class="special">(</span><span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span><span class="special">)</span> 344<span class="special">{</span> 345 <span class="keyword">return</span> <span class="special">(</span><span class="identifier">null_ok</span><span class="special"><</span><span class="identifier">T</span><span class="special">>*)</span><span class="identifier">p</span><span class="special">;</span> 346<span class="special">}</span> 347</pre> 348</div> 349</div> 350<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 351<td align="left"></td> 352<td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2015 David Abrahams, Stefan Seefeld<p> 353 Distributed under the Boost Software License, Version 1.0. (See accompanying 354 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> 355 </p> 356</div></td> 357</tr></table> 358<hr> 359<div class="spirit-nav"> 360<a accesskey="p" href="boost_python_pointee_hpp.html"><img src="../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../utility_and_infrastructure.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_type_id_hpp.html"><img src="../../images/next.png" alt="Next"></a> 361</div> 362</body> 363</html> 364
