1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Wait 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="TimeTraits.html" title="Time traits requirements"> 10<link rel="next" href="WaitTraits.html" title="Wait traits 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="TimeTraits.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="WaitTraits.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.WaitHandler"></a><a class="link" href="WaitHandler.html" title="Wait handler requirements">Wait handler requirements</a> 28</h3></div></div></div> 29<p> 30 A wait handler must meet the requirements for a <a class="link" href="Handler.html" title="Handlers">handler</a>. 31 A value <code class="computeroutput">h</code> of a wait handler class should work correctly in the 32 expression <code class="computeroutput">h(ec)</code>, where <code class="computeroutput">ec</code> is an lvalue of type 33 <code class="computeroutput">const error_code</code>. 34 </p> 35<h5> 36<a name="boost_asio.reference.WaitHandler.h0"></a> 37 <span class="phrase"><a name="boost_asio.reference.WaitHandler.examples"></a></span><a class="link" href="WaitHandler.html#boost_asio.reference.WaitHandler.examples">Examples</a> 38 </h5> 39<p> 40 A free function as a wait handler: 41 </p> 42<pre class="programlisting">void wait_handler( 43 const boost::system::error_code& ec) 44{ 45 ... 46} 47</pre> 48<p> 49 A wait handler function object: 50 </p> 51<pre class="programlisting">struct wait_handler 52{ 53 ... 54 void operator()( 55 const boost::system::error_code& ec) 56 { 57 ... 58 } 59 ... 60}; 61</pre> 62<p> 63 A lambda as a wait handler: 64 </p> 65<pre class="programlisting">socket.async_wait(..., 66 [](const boost::system::error_code& ec) 67 { 68 ... 69 }); 70</pre> 71<p> 72 A non-static class member function adapted to a wait handler using <code class="computeroutput">std::bind()</code>: 73 </p> 74<pre class="programlisting">void my_class::wait_handler( 75 const boost::system::error_code& ec) 76{ 77 ... 78} 79... 80socket.async_wait(..., 81 std::bind(&my_class::wait_handler, 82 this, std::placeholders::_1)); 83</pre> 84<p> 85 A non-static class member function adapted to a wait handler using <code class="computeroutput">boost::bind()</code>: 86 </p> 87<pre class="programlisting">void my_class::wait_handler( 88 const boost::system::error_code& ec) 89{ 90 ... 91} 92... 93socket.async_wait(..., 94 boost::bind(&my_class::wait_handler, 95 this, boost::asio::placeholders::error)); 96</pre> 97</div> 98<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 99<td align="left"></td> 100<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 101 Kohlhoff<p> 102 Distributed under the Boost Software License, Version 1.0. (See accompanying 103 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>) 104 </p> 105</div></td> 106</tr></table> 107<hr> 108<div class="spirit-nav"> 109<a accesskey="p" href="TimeTraits.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="WaitTraits.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 110</div> 111</body> 112</html> 113
