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| <div><h2 class="title"> |
| <a name="scope_exit"></a>Chapter 1. Boost.ScopeExit 1.1.0</h2></div> |
| <div><div class="author"><h3 class="author"> |
| <span class="firstname">Alexander</span> <span class="surname">Nasonov</span> |
| </h3></div></div> |
| <div><div class="author"><h3 class="author"> |
| <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> |
| </h3></div></div> |
| <div><p class="copyright">Copyright © 2006-2012 Alexander Nasonov, Lorenzo Caminiti</p></div> |
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| <a name="scope_exit.legal"></a><p> |
| Distributed under the Boost Software License, Version 1.0 (see accompanying |
| 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>) |
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| <p><b>Table of Contents</b></p> |
| <dl> |
| <dt><span class="section"><a href="index.html#scope_exit.introduction">Introduction</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/getting_started.html">Getting Started</a></span></dt> |
| <dd><dl> |
| <dt><span class="section"><a href="scope_exit/getting_started.html#scope_exit.getting_started.this_documentation">This Documentation</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/getting_started.html#scope_exit.getting_started.compilers_and_platforms">Compilers |
| and Platforms</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/getting_started.html#scope_exit.getting_started.installation">Installation</a></span></dt> |
| </dl></dd> |
| <dt><span class="section"><a href="scope_exit/tutorial.html">Tutorial</a></span></dt> |
| <dd><dl> |
| <dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_variables">Capturing Variables</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_the_object__this_">Capturing |
| The Object <code class="computeroutput"><span class="keyword">this</span></code></a></span></dt> |
| <dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_no_variable">Capturing |
| No Variable</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.capturing_all_variables__c__11_only_">Capturing |
| All Variables (C++11 Only)</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.template_workaround__gcc_">Template |
| Workaround (GCC)</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/tutorial.html#scope_exit.tutorial.same_line_expansions">Same Line Expansions</a></span></dt> |
| </dl></dd> |
| <dt><span class="section"><a href="scope_exit/alternatives.html">Annex: Alternatives</a></span></dt> |
| <dt><span class="section"><a href="scope_exit/no_variadic_macros.html">Annex: No Variadic Macros</a></span></dt> |
| <dt><span class="section"><a href="reference.html">Reference</a></span></dt> |
| <dd><dl><dt><span class="section"><a href="reference.html#header.boost.scope_exit_hpp">Header <boost/scope_exit.hpp></a></span></dt></dl></dd> |
| <dt><span class="section"><a href="scope_exit/acknowledgements.html">Acknowledgements</a></span></dt> |
| </dl> |
| </div> |
| <p> |
| This library allows to execute arbitrary code when the enclosing scope exits. |
| </p> |
| <div class="section scope_exit_introduction"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="scope_exit.introduction"></a><a class="link" href="index.html#scope_exit.introduction" title="Introduction">Introduction</a> |
| </h2></div></div></div> |
| <p> |
| Nowadays, every C++ developer is familiar with the Resource Acquisition Is |
| Initialization (<a href="http://www.research.att.com/~bs/glossary.html#Gresource-acquisition-is-initialization" target="_top">RAII</a>) |
| technique. It binds resource acquisition and release to initialization and |
| destruction of a variable that holds the resource. There are times when writing |
| a special class for such a variable is not worth the effort. This is when |
| <a class="link" href="index.html" title="Chapter 1. Boost.ScopeExit 1.1.0">Boost.ScopeExit</a> comes into play. |
| </p> |
| <p> |
| Programmers can put resource acquisition directly in their code and next to |
| it, they can write code that releases the resource using this library. For |
| example (see also <a href="../../test/world.cpp" target="_top"><code class="literal">world.cpp</code></a>): |
| <sup>[<a name="scope_exit.introduction.f0" href="#ftn.scope_exit.introduction.f0" class="footnote">1</a>]</sup> |
| </p> |
| <p> |
| </p> |
| <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> |
| <span class="keyword">bool</span> <span class="identifier">commit</span> <span class="special">=</span> <span class="keyword">false</span><span class="special">;</span> |
| |
| <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> |
| <span class="comment">// Following block is executed when the enclosing scope exits.</span> |
| <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> |
| <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> |
| <span class="special">}</span> <span class="identifier">BOOST_SCOPE_EXIT_END</span> |
| |
| <span class="comment">// ... // (3) other operations</span> |
| |
| <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> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| </div> |
| <div class="footnotes"> |
| <br><hr width="100" align="left"> |
| <div class="footnote"><p><sup>[<a id="ftn.scope_exit.introduction.f0" href="#scope_exit.introduction.f0" class="para">1</a>] </sup> |
| Older versions of this library used a <a href="http://www.boost.org/libs/preprocessor" target="_top">Boost.Preprocessor</a> |
| sequence to specify the list of captured variables. While maintaining full |
| backward compatibility, it is now possible to specify the captured variables |
| also using a comma-separated list (which is the preferred syntax). See the |
| <a class="link" href="scope_exit/no_variadic_macros.html" title="Annex: No Variadic Macros">No Variadic Macros</a> section |
| for more information. |
| </p></div> |
| </div> |
| </div> |
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| <td align="left"><p><small>Last revised: April 28, 2012 at 01:48:44 GMT</small></p></td> |
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