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   4 <title>Class template function</title>
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  18 <div class="refentry">
  19 <a name="boost.log.attributes.function"></a><div class="titlepage"></div>
  20 <div class="refnamediv">
  21 <h2><span class="refentrytitle">Class template function</span></h2>
  22 <p>boost::log::attributes::function &#8212; A class of an attribute that acquires its value from a third-party function object. </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: &lt;<a class="link" href="../../../attributes.html#header.boost.log.attributes.function_hpp" title="Header &lt;boost/log/attributes/function.hpp&gt;">boost/log/attributes/function.hpp</a>&gt;
  26
  27 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> R<span class="special">&gt;</span>
  28 <span class="keyword">class</span> <a class="link" href="function.html" title="Class template function">function</a> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">attribute</span> <span class="special">{</span>
  29 <span class="keyword">public</span><span class="special">:</span>
  30   <span class="comment">// types</span>
  31   <span class="keyword">typedef</span> <span class="identifier">R</span> <a name="boost.log.attributes.function.value_type"></a><span class="identifier">value_type</span><span class="special">;</span>  <span class="comment">// The attribute value type. </span>
  32
  33   <span class="comment">// member classes/structs/unions</span>
  34
  35   <span class="comment">// Base class for factory implementation.</span>
  36
  37   <span class="keyword">class</span> <a class="link" href="function/impl.html" title="Class impl">impl</a> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">attribute</span><span class="special">::</span><span class="identifier">impl</span> <span class="special">{</span>
  38   <span class="special">}</span><span class="special">;</span>
  39
  40   <span class="comment">// Factory implementation.</span>
  41   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span>
  42   <span class="keyword">class</span> <a class="link" href="function/impl_template.html" title="Class template impl_template">impl_template</a> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">function</span><span class="special">&lt;</span> <span class="identifier">R</span> <span class="special">&gt;</span><span class="special">::</span><span class="identifier">impl</span> <span class="special">{</span>
  43   <span class="keyword">public</span><span class="special">:</span>
  44     <span class="comment">// <a class="link" href="function/impl_template.html#boost.log.attributes.function.impl_templateconstruct-copy-destruct">construct/copy/destruct</a></span>
  45     <span class="keyword">explicit</span> <a class="link" href="function/impl_template.html#idp35416064-bb"><span class="identifier">impl_template</span></a><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  46
  47     <span class="comment">// <a class="link" href="function/impl_template.html#idp35413168-bb">public member functions</a></span>
  48     <span class="keyword">virtual</span> <a class="link" href="../attribute_value.html" title="Class attribute_value">attribute_value</a> <a class="link" href="function/impl_template.html#idp35413728-bb"><span class="identifier">get_value</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  49   <span class="special">}</span><span class="special">;</span>
  50
  51   <span class="comment">// <a class="link" href="function.html#boost.log.attributes.functionconstruct-copy-destruct">construct/copy/destruct</a></span>
  52   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">explicit</span> <a class="link" href="function.html#idp35419632-bb"><span class="identifier">function</span></a><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  53   <span class="keyword">explicit</span> <a class="link" href="function.html#idp35422160-bb"><span class="identifier">function</span></a><span class="special">(</span><a class="link" href="cast_source.html" title="Class cast_source">cast_source</a> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  54 <span class="special">}</span><span class="special">;</span></pre></div>
  55 <div class="refsect1">
  56 <a name="idp90405328"></a><h2>Description</h2>
  57 <p>The attribute calls a stored nullary function object to acquire each value. The result type of the function object is the attribute value type.</p>
  58 <p>It is not recommended to use this class directly. Use <code class="computeroutput">make_function</code> convenience functions to construct the attribute instead. </p>
  59 <div class="refsect2">
  60 <a name="idp90407168"></a><h3>
  61 <a name="boost.log.attributes.functionconstruct-copy-destruct"></a><code class="computeroutput">function</code>
  62         public
  63        construct/copy/destruct</h3>
  64 <div class="orderedlist"><ol class="orderedlist" type="1">
  65 <li class="listitem">
  66 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">explicit</span> <a name="idp35419632-bb"></a><span class="identifier">function</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&amp;</span> fun<span class="special">)</span><span class="special">;</span></pre>
  67 <p>Initializing constructor </p>
  68 </li>
  69 <li class="listitem">
  70 <pre class="literallayout"><span class="keyword">explicit</span> <a name="idp35422160-bb"></a><span class="identifier">function</span><span class="special">(</span><a class="link" href="cast_source.html" title="Class cast_source">cast_source</a> <span class="keyword">const</span> <span class="special">&amp;</span> source<span class="special">)</span><span class="special">;</span></pre>
  71 <p>Constructor for casting support </p>
  72 </li>
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  79 <td align="right"><div class="copyright-footer">Copyright &#169; 2007-2014 Andrey Semashev<p>
  80         Distributed under the Boost Software License, Version 1.0. (See accompanying
  81         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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