1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Struct template extract_or_throw</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="../../../index.html" title="Chapter 1. Boost.Log v2"> 8<link rel="up" href="../../../attributes.html#header.boost.log.attributes.value_extraction_fwd_hpp" title="Header <boost/log/attributes/value_extraction_fwd.hpp>"> 9<link rel="prev" href="extract_or_default.html" title="Struct template extract_or_default"> 10<link rel="next" href="../value_extractor.html" title="Class template value_extractor"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td></tr></table> 14<hr> 15<div class="spirit-nav"> 16<a accesskey="p" href="extract_or_default.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../attributes.html#header.boost.log.attributes.value_extraction_fwd_hpp"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../value_extractor.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 17</div> 18<div class="refentry"> 19<a name="boost.log.result_of.extract_or_throw"></a><div class="titlepage"></div> 20<div class="refnamediv"> 21<h2><span class="refentrytitle">Struct template extract_or_throw</span></h2> 22<p>boost::log::result_of::extract_or_throw — A metafunction that allows to acquire the result of the value extraction. </p> 23</div> 24<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 25<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../../attributes.html#header.boost.log.attributes.value_extraction_fwd_hpp" title="Header <boost/log/attributes/value_extraction_fwd.hpp>">boost/log/attributes/value_extraction_fwd.hpp</a>> 26 27</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">,</span> <span class="keyword">typename</span> TagT<span class="special">></span> 28<span class="keyword">struct</span> <a class="link" href="extract_or_throw.html" title="Struct template extract_or_throw">extract_or_throw</a> <span class="special">{</span> 29<span class="special">}</span><span class="special">;</span></pre></div> 30<div class="refsect1"> 31<a name="idm44984879945840"></a><h2>Description</h2> 32<p>The metafunction results in a type that is in form of <code class="computeroutput">T const&</code>, if <code class="computeroutput">T</code> is not an MPL type sequence, or <code class="computeroutput">value_ref< T, TagT ></code> otherwise. In the latter case the value reference shall never be empty. </p> 33</div> 34</div> 35<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 36<td align="left"></td> 37<td align="right"><div class="copyright-footer">Copyright © 2007-2019 Andrey Semashev<p> 38 Distributed under the Boost Software License, Version 1.0. (See accompanying 39 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>). 40 </p> 41</div></td> 42</tr></table> 43<hr> 44<div class="spirit-nav"> 45<a accesskey="p" href="extract_or_default.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../attributes.html#header.boost.log.attributes.value_extraction_fwd_hpp"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../value_extractor.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 46</div> 47</body> 48</html> 49
