doc/html/boost_asio/reference/ResolveHandler.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   4 <title>Resolve handler requirements</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="../../boost_asio.html" title="Boost.Asio">
   8 <link rel="up" href="../reference.html" title="Reference">
   9 <link rel="prev" href="ReadHandler.html" title="Read handler requirements">
  10 <link rel="next" href="ResolverService.html" title="Resolver service requirements">
  11 </head>
  12 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  13 <table cellpadding="2" width="100%"><tr>
  14 <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
  15 <td align="center"><a href="../../../../index.html">Home</a></td>
  16 <td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
  17 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  18 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  19 <td align="center"><a href="../../../../more/index.htm">More</a></td>
  20 </tr></table>
  21 <hr>
  22 <div class="spirit-nav">
  23 <a accesskey="p" href="ReadHandler.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../boost_asio.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="ResolverService.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  24 </div>
  25 <div class="section">
  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_asio.reference.ResolveHandler"></a><a class="link" href="ResolveHandler.html" title="Resolve handler requirements">Resolve handler
  28       requirements</a>
  29 </h3></div></div></div>
  30 <p>
  31         A resolve handler must meet the requirements for a <a class="link" href="Handler.html" title="Handlers">handler</a>.
  32         A value <code class="computeroutput"><span class="identifier">h</span></code> of a resolve handler
  33         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>
  34         <span class="identifier">i</span><span class="special">)</span></code>,
  35         where <code class="computeroutput"><span class="identifier">ec</span></code> is an lvalue of
  36         type <code class="computeroutput"><span class="keyword">const</span> <span class="identifier">error_code</span></code>
  37         and <code class="computeroutput"><span class="identifier">i</span></code> is an lvalue of type
  38         <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>
  39         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
  40         initiate the asynchronous operation.
  41       </p>
  42 <h5>
  43 <a name="boost_asio.reference.ResolveHandler.h0"></a>
  44         <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>
  45       </h5>
  46 <p>
  47         A free function as a resolve handler:
  48       </p>
  49 <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">resolve_handler</span><span class="special">(</span>
  50     <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>
  51     <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>
  52 <span class="special">{</span>
  53   <span class="special">...</span>
  54 <span class="special">}</span>
  55 </pre>
  56 <p>
  57         A resolve handler function object:
  58       </p>
  59 <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">resolve_handler</span>
  60 <span class="special">{</span>
  61   <span class="special">...</span>
  62   <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span>
  63       <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>
  64       <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>
  65   <span class="special">{</span>
  66     <span class="special">...</span>
  67   <span class="special">}</span>
  68   <span class="special">...</span>
  69 <span class="special">};</span>
  70 </pre>
  71 <p>
  72         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>:
  73       </p>
  74 <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>
  75     <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>
  76     <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>
  77 <span class="special">{</span>
  78   <span class="special">...</span>
  79 <span class="special">}</span>
  80 <span class="special">...</span>
  81 <span class="identifier">resolver</span><span class="special">.</span><span class="identifier">async_resolve</span><span class="special">(...,</span>
  82     <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>
  83       <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>
  84       <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>
  85 </pre>
  86 </div>
  87 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
  88 <td align="left"></td>
  89 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2017 Christopher M. Kohlhoff<p>
  90         Distributed under the Boost Software License, Version 1.0. (See accompanying
  91         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>)
  92       </p>
  93 </div></td>
  94 </tr></table>
  95 <hr>
  96 <div class="spirit-nav">
  97 <a accesskey="p" href="ReadHandler.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../boost_asio.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="ResolverService.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  98 </div>
  99 </body>
 100 </html>