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<title>Service requirements</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.Service"></a><a class="link" href="Service.html" title="Service requirements">Service requirements</a>
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<p>
        A class is a service if it is publicly derived from another service, or if
        it is a class derived from <code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">service</span></code>
        and contains a publicly-accessible declaration as follows:
      </p>
<pre class="programlisting"><span class="keyword">static</span> <span class="identifier">io_service</span><span class="special">::</span><span class="identifier">id</span> <span class="identifier">id</span><span class="special">;</span>
</pre>
<p>
        All services define a one-argument constructor that takes a reference to
        the <code class="computeroutput"><span class="identifier">io_service</span></code> object that
        owns the service. This constructor is <span class="emphasis"><em>explicit</em></span>, preventing
        its participation in automatic conversions. For example:
      </p>
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">my_service</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">io_service</span><span class="special">::</span><span class="identifier">service</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
  <span class="keyword">static</span> <span class="identifier">io_service</span><span class="special">::</span><span class="identifier">id</span> <span class="identifier">id</span><span class="special">;</span>
  <span class="keyword">explicit</span> <span class="identifier">my_service</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">&amp;</span> <span class="identifier">ios</span><span class="special">);</span>
<span class="keyword">private</span><span class="special">:</span>
  <span class="keyword">virtual</span> <span class="keyword">void</span> <span class="identifier">shutdown_service</span><span class="special">();</span>
  <span class="special">...</span>
<span class="special">};</span>
</pre>
<p>
        A service's <code class="computeroutput"><span class="identifier">shutdown_service</span></code>
        member function must cause all copies of user-defined handler objects that
        are held by the service to be destroyed.
      </p>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2014 Christopher M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        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>)
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