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<title>Function template extract_or_throw</title>
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<h2><span class="refentrytitle">Function template extract_or_throw</span></h2>
<p>boost::log::extract_or_throw</p>
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<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<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_hpp" title="Header <boost/log/attributes/value_extraction.hpp>">boost/log/attributes/value_extraction.hpp</a>>
</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> <span class="keyword">void</span><span class="special">></span>
<a class="link" href="result_of/extract_or_throw.html" title="Struct template extract_or_throw">result_of::extract_or_throw</a><span class="special"><</span> <span class="identifier">T</span><span class="special">,</span> <span class="identifier">TagT</span> <span class="special">></span><span class="special">::</span><span class="identifier">type</span>
<span class="identifier">extract_or_throw</span><span class="special">(</span><a class="link" href="attribute_name.html" title="Class attribute_name">attribute_name</a> <span class="keyword">const</span> <span class="special">&</span> name<span class="special">,</span> <span class="identifier">record</span> <span class="keyword">const</span> <span class="special">&</span> rec<span class="special">)</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idp109933456"></a><h2>Description</h2>
<p>The function extracts an attribute value from the view. The user has to explicitly specify the type or set of possible types of the attribute value to be extracted.</p>
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<td><p><span class="term">Parameters:</span></p></td>
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<td><p><span class="term"><code class="computeroutput">name</code></span></p></td>
<td><p>The name of the attribute value to extract. </p></td>
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<td><p><span class="term"><code class="computeroutput">rec</code></span></p></td>
<td><p>A log record. The attribute value will be sought among those associated with the record. </p></td>
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<td><p><span class="term">Returns:</span></p></td>
<td><p>The extracted value or a non-empty <code class="computeroutput">value_ref</code> that refers to the value. </p></td>
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<td><p><span class="term">Throws:</span></p></td>
<td>An exception is thrown if the requested value cannot be extracted. </td>
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<td align="right"><div class="copyright-footer">Copyright © 2007-2015 Andrey
Semashev<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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