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<title>Resolve handler requirements</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.ResolveHandler"></a><a class="link" href="ResolveHandler.html" title="Resolve handler requirements">Resolve handler
      requirements</a>
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<p>
        A resolve handler must meet the requirements for a <a class="link" href="Handler.html" title="Handlers">handler</a>.
        A value <code class="computeroutput"><span class="identifier">h</span></code> of a resolve handler
        class should work correctly in the expression <code class="computeroutput"><span class="identifier">h</span><span class="special">(</span><span class="identifier">ec</span><span class="special">,</span>
        <span class="identifier">i</span><span class="special">)</span></code>,
        where <code class="computeroutput"><span class="identifier">ec</span></code> is an lvalue of
        type <code class="computeroutput"><span class="keyword">const</span> <span class="identifier">error_code</span></code>
        and <code class="computeroutput"><span class="identifier">i</span></code> is an lvalue of type
        <code class="computeroutput"><span class="keyword">const</span> <span class="identifier">ip</span><span class="special">::</span><span class="identifier">basic_resolver_iterator</span><span class="special">&lt;</span><span class="identifier">InternetProtocol</span><span class="special">&gt;</span></code>. <code class="computeroutput"><span class="identifier">InternetProtocol</span></code>
        is the template parameter of the <a class="link" href="ip__resolver_service.html" title="ip::resolver_service"><code class="computeroutput"><span class="identifier">resolver_service</span></code></a> which is used to
        initiate the asynchronous operation.
      </p>
<h5>
<a name="boost_asio.reference.ResolveHandler.h0"></a>
        <span class="phrase"><a name="boost_asio.reference.ResolveHandler.examples"></a></span><a class="link" href="ResolveHandler.html#boost_asio.reference.ResolveHandler.examples">Examples</a>
      </h5>
<p>
        A free function as a resolve handler:
      </p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">resolve_handler</span><span class="special">(</span>
    <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">ec</span><span class="special">,</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">iterator</span><span class="special">)</span>
<span class="special">{</span>
  <span class="special">...</span>
<span class="special">}</span>
</pre>
<p>
        A resolve handler function object:
      </p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">resolve_handler</span>
<span class="special">{</span>
  <span class="special">...</span>
  <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span>
      <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">ec</span><span class="special">,</span>
      <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">iterator</span><span class="special">)</span>
  <span class="special">{</span>
    <span class="special">...</span>
  <span class="special">}</span>
  <span class="special">...</span>
<span class="special">};</span>
</pre>
<p>
        A non-static class member function adapted to a resolve handler using <code class="computeroutput"><span class="identifier">bind</span><span class="special">()</span></code>:
      </p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">my_class</span><span class="special">::</span><span class="identifier">resolve_handler</span><span class="special">(</span>
    <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">ec</span><span class="special">,</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">resolver</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">iterator</span><span class="special">)</span>
<span class="special">{</span>
  <span class="special">...</span>
<span class="special">}</span>
<span class="special">...</span>
<span class="identifier">resolver</span><span class="special">.</span><span class="identifier">async_resolve</span><span class="special">(...,</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(&amp;</span><span class="identifier">my_class</span><span class="special">::</span><span class="identifier">resolve_handler</span><span class="special">,</span>
      <span class="keyword">this</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">placeholders</span><span class="special">::</span><span class="identifier">error</span><span class="special">,</span>
      <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">placeholders</span><span class="special">::</span><span class="identifier">iterator</span><span class="special">));</span>
</pre>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2015 Christopher M.
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