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<title>Chapter&#160;1.&#160;Boost.ScopeExit 1.1.0</title>
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<div><h2 class="title">
<a name="scope_exit"></a>Chapter&#160;1.&#160;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">&lt;<a class="email" href="mailto:lorcaminiti@gmail.com">lorcaminiti@gmail.com</a>&gt;</code></span>
</h3></div></div>
<div><p class="copyright">Copyright &#169; 2006-2012 Alexander Nasonov, Lorenzo Caminiti</p></div>
<div><div class="legalnotice">
<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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<div class="toc">
<p><b>Table of Contents</b></p>
<dl class="toc">
<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>
<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">
<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&#160;1.&#160;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>):
      <a href="#ftn.scope_exit.introduction.f0" class="footnote" name="scope_exit.introduction.f0"><sup class="footnote">[1]</sup></a>
    </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">&amp;</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">(&amp;</span><span class="identifier">commit</span><span class="special">,</span> <span class="special">&amp;</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 style="width:100; text-align:left;margin-left: 0">
<div id="ftn.scope_exit.introduction.f0" class="footnote"><p><a href="#scope_exit.introduction.f0" class="para"><sup class="para">[1] </sup></a>
        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>
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