1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Macro BOOST_TTI_HAS_DATA</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. The Type Traits Introspection Library"> 8<link rel="up" href="header/boost/tti/has_data_hpp.html" title="Header <boost/tti/has_data.hpp>"> 9<link rel="prev" href="BOOST_TTI_TRAIT_HAS_DATA.html" title="Macro BOOST_TTI_TRAIT_HAS_DATA"> 10<link rel="next" href="header/boost/tti/has_enum_hpp.html" title="Header <boost/tti/has_enum.hpp>"> 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="BOOST_TTI_TRAIT_HAS_DATA.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="header/boost/tti/has_data_hpp.html"><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="header/boost/tti/has_enum_hpp.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="refentry"> 26<a name="BOOST_TTI_HAS_DATA"></a><div class="titlepage"></div> 27<div class="refnamediv"> 28<h2><span class="refentrytitle">Macro BOOST_TTI_HAS_DATA</span></h2> 29<p>BOOST_TTI_HAS_DATA — A macro which expands to a metafunction which tests whether member data or static member data with a particular name and type exists. </p> 30</div> 31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 32<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="header/boost/tti/has_data_hpp.html" title="Header <boost/tti/has_data.hpp>">boost/tti/has_data.hpp</a>> 33 34</span>BOOST_TTI_HAS_DATA(name)</pre></div> 35<div class="refsect1"> 36<a name="idm45658025982560"></a><h2>Description</h2> 37<p>BOOST_TTI_HAS_DATA is a macro which expands to a metafunction. The metafunction tests whether member data or static member data with a particular name and type exists. The macro takes the form of BOOST_TTI_HAS_DATA(name) where</p> 38<p>name = the name of the inner data.</p> 39<p>BOOST_TTI_HAS_DATA generates a metafunction called "has_data_name" where 'name' is the macro parameter.</p> 40<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">BOOST_TTI_TP_T</span><span class="special">,</span><span class="keyword">class</span> <span class="identifier">BOOST_TTI_TP_TYPE</span><span class="special">></span> 41<span class="keyword">struct</span> <span class="identifier">has_data_</span><span class="char">'name'</span> 42 <span class="special">{</span> 43 <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">value</span> <span class="special">=</span> <span class="identifier">unspecified</span><span class="special">;</span> 44 <span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">bool_</span><span class="special"><</span><span class="keyword">true</span><span class="special">-</span><span class="identifier">or</span><span class="special">-</span><span class="keyword">false</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span> 45 <span class="special">}</span><span class="special">;</span> 46 47<span class="identifier">The</span> <span class="identifier">metafunction</span> <span class="identifier">types</span> <span class="identifier">and</span> <span class="keyword">return</span><span class="special">:</span> 48 49 <span class="identifier">BOOST_TTI_TP_T</span> <span class="special">=</span> <span class="identifier">the</span> <span class="identifier">enclosing</span> <span class="identifier">type</span> <span class="identifier">in</span> <span class="identifier">which</span> <span class="identifier">to</span> <span class="identifier">look</span> <span class="keyword">for</span> <span class="identifier">our</span> <span class="char">'name'</span> 50 <span class="identifier">The</span> <span class="identifier">enclosing</span> <span class="identifier">type</span> <span class="identifier">can</span> <span class="identifier">be</span> <span class="identifier">a</span> <span class="keyword">class</span><span class="special">,</span> <span class="keyword">struct</span><span class="special">,</span> <span class="identifier">or</span> <span class="keyword">union</span><span class="special">.</span> 51 <span class="identifier">If</span> <span class="identifier">the</span> <span class="identifier">type</span> <span class="identifier">is</span> <span class="identifier">a</span> <span class="keyword">union</span><span class="special">,</span> <span class="keyword">static</span> <span class="identifier">member</span> <span class="identifier">data</span> <span class="identifier">can</span> <span class="identifier">only</span> 52 <span class="identifier">be</span> <span class="identifier">found</span> <span class="keyword">if</span> <span class="identifier">the</span> <span class="identifier">C</span><span class="special">++</span><span class="number">11</span> <span class="identifier">unrestricted</span> <span class="keyword">union</span> <span class="identifier">is</span> <span class="identifier">implemented</span> 53 <span class="identifier">by</span> <span class="identifier">the</span> <span class="identifier">compiler</span> <span class="identifier">being</span> <span class="identifier">used</span><span class="special">,</span> <span class="identifier">since</span> <span class="identifier">prior</span> <span class="identifier">to</span> <span class="identifier">C</span><span class="special">++</span><span class="number">11</span> <span class="identifier">a</span> <span class="keyword">union</span> 54 <span class="identifier">could</span> <span class="identifier">not</span> <span class="identifier">have</span> <span class="keyword">static</span> <span class="identifier">data</span> <span class="identifier">members</span><span class="special">.</span> 55 56 <span class="identifier">BOOST_TTI_TP_TYPE</span> <span class="special">=</span> <span class="identifier">The</span> <span class="identifier">type</span> <span class="identifier">of</span> <span class="identifier">the</span> <span class="identifier">member</span> <span class="identifier">data</span> <span class="identifier">or</span> <span class="keyword">static</span> <span class="identifier">member</span><span class="special">.</span> 57 58 <span class="identifier">returns</span> <span class="special">=</span> <span class="char">'value'</span> <span class="identifier">is</span> <span class="keyword">true</span> <span class="keyword">if</span> <span class="identifier">the</span> <span class="char">'name'</span> <span class="identifier">exists</span><span class="special">,</span> <span class="identifier">with</span> <span class="identifier">the</span> <span class="identifier">correct</span> <span class="identifier">data</span> <span class="identifier">type</span><span class="special">,</span> 59 <span class="identifier">otherwise</span> <span class="char">'value'</span> <span class="identifier">is</span> <span class="keyword">false</span><span class="special">.</span> 60</pre> 61<p> </p> 62</div> 63</div> 64<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 65<td align="left"></td> 66<td align="right"><div class="copyright-footer">Copyright © 2011-2013 Tropic Software 67 East Inc<p> 68 Distributed under the Boost Software License, Version 1.0. (See accompanying 69 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>) 70 </p> 71</div></td> 72</tr></table> 73<hr> 74<div class="spirit-nav"> 75<a accesskey="p" href="BOOST_TTI_TRAIT_HAS_DATA.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="header/boost/tti/has_data_hpp.html"><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="header/boost/tti/has_enum_hpp.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 76</div> 77</body> 78</html> 79
