1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Chapter 1. Boost.ScopeExit 1.1.0</title> 5<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="index.html" title="Chapter 1. Boost.ScopeExit 1.1.0"> 8<link rel="next" href="scope_exit/getting_started.html" title="Getting Started"> 9</head> 10<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 11<table cellpadding="2" width="100%"><tr> 12<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 13<td align="center"><a href="../../../../index.html">Home</a></td> 14<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 15<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 16<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 17<td align="center"><a href="../../../../more/index.htm">More</a></td> 18</tr></table> 19<hr> 20<div class="spirit-nav"><a accesskey="n" href="scope_exit/getting_started.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a></div> 21<div class="chapter"> 22<div class="titlepage"><div> 23<div><h2 class="title"> 24<a name="scope_exit"></a>Chapter 1. Boost.ScopeExit 1.1.0</h2></div> 25<div><div class="author"><h3 class="author"> 26<span class="firstname">Alexander</span> <span class="surname">Nasonov</span> 27</h3></div></div> 28<div><div class="author"><h3 class="author"> 29<span class="firstname">Lorenzo</span> <span class="surname">Caminiti <code class="email"><<a class="email" href="mailto:lorcaminiti@gmail.com">lorcaminiti@gmail.com</a>></code></span> 30</h3></div></div> 31<div><p class="copyright">Copyright © 2006-2012 Alexander Nasonov, Lorenzo Caminiti</p></div> 32<div><div class="legalnotice"> 33<a name="scope_exit.legal"></a><p> 34 Distributed under the Boost Software License, Version 1.0 (see accompanying 35 file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 36 </p> 37</div></div> 38</div></div> 39<div class="toc"> 40<p><b>Table of Contents</b></p> 41<dl class="toc"> 42<dt><span class="section"><a href="index.html#scope_exit.introduction">Introduction</a></span></dt> 43<dt><span class="section"><a href="scope_exit/getting_started.html">Getting Started</a></span></dt> 44<dd><dl> 45<dt><span class="section"><a href="scope_exit/getting_started.html#scope_exit.getting_started.this_documentation">This Documentation</a></span></dt> 46<dt><span class="section"><a href="scope_exit/getting_started.html#scope_exit.getting_started.compilers_and_platforms">Compilers 47 and Platforms</a></span></dt> 48<dt><span class="section"><a href="scope_exit/getting_started.html#scope_exit.getting_started.installation">Installation</a></span></dt> 49</dl></dd> 50<dt><span class="section"><a href="scope_exit/tutorial.html">Tutorial</a></span></dt> 51<dd><dl> 52<dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_variables">Capturing Variables</a></span></dt> 53<dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_the_object__this_">Capturing 54 The Object <code class="computeroutput"><span class="keyword">this</span></code></a></span></dt> 55<dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_no_variable">Capturing 56 No Variable</a></span></dt> 57<dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_all_variables__c__11_only_">Capturing 58 All Variables (C++11 Only)</a></span></dt> 59<dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.template_workaround__gcc_">Template 60 Workaround (GCC)</a></span></dt> 61<dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.same_line_expansions">Same Line Expansions</a></span></dt> 62</dl></dd> 63<dt><span class="section"><a href="scope_exit/alternatives.html">Annex: Alternatives</a></span></dt> 64<dt><span class="section"><a href="scope_exit/no_variadic_macros.html">Annex: No Variadic Macros</a></span></dt> 65<dt><span class="section"><a href="reference.html">Reference</a></span></dt> 66<dt><span class="section"><a href="scope_exit/acknowledgements.html">Acknowledgements</a></span></dt> 67</dl> 68</div> 69<p> 70 This library allows to execute arbitrary code when the enclosing scope exits. 71 </p> 72<div class="section"> 73<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 74<a name="scope_exit.introduction"></a><a class="link" href="index.html#scope_exit.introduction" title="Introduction">Introduction</a> 75</h2></div></div></div> 76<p> 77 Nowadays, every C++ developer is familiar with the Resource Acquisition Is 78 Initialization (<a href="http://www.research.att.com/~bs/glossary.html#Gresource-acquisition-is-initialization" target="_top">RAII</a>) 79 technique. It binds resource acquisition and release to initialization and 80 destruction of a variable that holds the resource. There are times when writing 81 a special class for such a variable is not worth the effort. This is when 82 <a class="link" href="index.html" title="Chapter 1. Boost.ScopeExit 1.1.0">Boost.ScopeExit</a> comes into play. 83 </p> 84<p> 85 Programmers can put resource acquisition directly in their code and next to 86 it, they can write code that releases the resource using this library. For 87 example (see also <a href="../../test/world.cpp" target="_top"><code class="literal">world.cpp</code></a>): 88 <a href="#ftn.scope_exit.introduction.f0" class="footnote" name="scope_exit.introduction.f0"><sup class="footnote">[1]</sup></a> 89 </p> 90<p> 91</p> 92<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">world</span><span class="special">::</span><span class="identifier">add_person</span><span class="special">(</span><span class="identifier">person</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">a_person</span><span class="special">)</span> <span class="special">{</span> 93 <span class="keyword">bool</span> <span class="identifier">commit</span> <span class="special">=</span> <span class="keyword">false</span><span class="special">;</span> 94 95 <span class="identifier">persons_</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">a_person</span><span class="special">);</span> <span class="comment">// (1) direct action</span> 96 <span class="comment">// Following block is executed when the enclosing scope exits.</span> 97 <span class="identifier">BOOST_SCOPE_EXIT</span><span class="special">(&</span><span class="identifier">commit</span><span class="special">,</span> <span class="special">&</span><span class="identifier">persons_</span><span class="special">)</span> <span class="special">{</span> 98 <span class="keyword">if</span><span class="special">(!</span><span class="identifier">commit</span><span class="special">)</span> <span class="identifier">persons_</span><span class="special">.</span><span class="identifier">pop_back</span><span class="special">();</span> <span class="comment">// (2) rollback action</span> 99 <span class="special">}</span> <span class="identifier">BOOST_SCOPE_EXIT_END</span> 100 101 <span class="comment">// ... // (3) other operations</span> 102 103 <span class="identifier">commit</span> <span class="special">=</span> <span class="keyword">true</span><span class="special">;</span> <span class="comment">// (4) disable rollback actions</span> 104<span class="special">}</span> 105</pre> 106<p> 107 </p> 108</div> 109<div class="footnotes"> 110<br><hr style="width:100; text-align:left;margin-left: 0"> 111<div id="ftn.scope_exit.introduction.f0" class="footnote"><p><a href="#scope_exit.introduction.f0" class="para"><sup class="para">[1] </sup></a> 112 Older versions of this library used a <a href="http://www.boost.org/libs/preprocessor" target="_top">Boost.Preprocessor</a> 113 sequence to specify the list of captured variables. While maintaining full 114 backward compatibility, it is now possible to specify the captured variables 115 also using a comma-separated list (which is the preferred syntax). See the 116 <a class="link" href="scope_exit/no_variadic_macros.html" title="Annex: No Variadic Macros">No Variadic Macros</a> section 117 for more information. 118 </p></div> 119</div> 120</div> 121<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 122<td align="left"><p><small>Last revised: August 11, 2020 at 14:59:35 GMT</small></p></td> 123<td align="right"><div class="copyright-footer"></div></td> 124</tr></table> 125<hr> 126<div class="spirit-nav"><a accesskey="n" href="scope_exit/getting_started.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a></div> 127</body> 128</html> 129
