<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Function any_cast</title> <link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../../boost_typeerasure/reference.html#header.boost.type_erasure.any_cast_hpp" title="Header <boost/type_erasure/any_cast.hpp>"> <link rel="prev" href="constructible.html" title="Struct template constructible"> <link rel="next" href="dynamic_binding.html" title="Class template dynamic_binding"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" 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name="boost.type_erasure.any_cast_idm45506900398752"></a><div class="titlepage"></div> <div class="refnamediv"> <h2><span class="refentrytitle">Function any_cast</span></h2> <p>boost::type_erasure::any_cast</p> </div> <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="../../boost_typeerasure/reference.html#header.boost.type_erasure.any_cast_hpp" title="Header <boost/type_erasure/any_cast.hpp>">boost/type_erasure/any_cast.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> Concept<span class="special">,</span> <span class="keyword">typename</span> Tag<span class="special">></span> <span class="identifier">T</span> <span class="identifier">any_cast</span><span class="special">(</span><a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">Tag</span> <span class="special">></span> <span class="special">&</span> arg<span class="special">)</span><span class="special">;</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> Concept<span class="special">,</span> <span class="keyword">typename</span> Tag<span class="special">></span> <span class="identifier">T</span> <span class="identifier">any_cast</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">Tag</span> <span class="special">></span> <span class="special">&</span> arg<span class="special">)</span><span class="special">;</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> Concept<span class="special">,</span> <span class="keyword">typename</span> Tag<span class="special">></span> <span class="identifier">T</span> <span class="identifier">any_cast</span><span class="special">(</span><a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">Tag</span> <span class="special">></span> <span class="special">*</span> arg<span class="special">)</span><span class="special">;</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> Concept<span class="special">,</span> <span class="keyword">typename</span> Tag<span class="special">></span> <span class="identifier">T</span> <span class="identifier">any_cast</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">Tag</span> <span class="special">></span> <span class="special">*</span> arg<span class="special">)</span><span class="special">;</span></pre></div> <div class="refsect1"> <a name="idm45555079768048"></a><h2>Description</h2> <p>Attempts to extract the object that <code class="computeroutput">arg</code> holds. If casting to a pointer fails, <code class="computeroutput"><a class="link" href="any_cast_idm45506900398752.html" title="Function any_cast">any_cast</a></code> returns a null pointer. Casting to <code class="computeroutput">void*</code> always succeeds and returns the address of stored object.</p> <pre class="programlisting"><span class="identifier">any</span><span class="special"><</span><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">typeid_</span><span class="special"><</span><span class="special">></span><span class="special">,</span> <span class="identifier">copy_constructible</span><span class="special"><</span><span class="special">></span> <span class="special">></span> <span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">1</span><span class="special">)</span><span class="special">;</span> <span class="identifier">any_cast</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span><span class="special">;</span> <span class="comment">// returns 1</span> <span class="identifier">any_cast</span><span class="special"><</span><span class="keyword">int</span><span class="special">&</span><span class="special">></span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span><span class="special">;</span> <span class="comment">// returns a reference to the contents of x</span> <span class="identifier">any_cast</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span><span class="special">;</span> <span class="comment">// throws bad_any_cast</span> <span class="identifier">any_cast</span><span class="special"><</span><span class="keyword">int</span><span class="special">*</span><span class="special">></span><span class="special">(</span><span class="special">&</span><span class="identifier">x</span><span class="special">)</span><span class="special">;</span> <span class="comment">// returns a pointer to the contents of x</span> <span class="identifier">any_cast</span><span class="special"><</span><span class="keyword">void</span><span class="special">*</span><span class="special">></span><span class="special">(</span><span class="special">&</span><span class="identifier">x</span><span class="special">)</span><span class="special">;</span> <span class="comment">// returns a pointer to the contents of x</span> <span class="identifier">any_cast</span><span class="special"><</span><span class="keyword">double</span><span class="special">*</span><span class="special">></span><span class="special">(</span><span class="special">&</span><span class="identifier">x</span><span class="special">)</span><span class="special">;</span> <span class="comment">// returns NULL</span> </pre> <p> </p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody> <tr> <td><p><span class="term">Requires:</span></p></td> <td><p>if <code class="computeroutput">arg</code> is a pointer, <code class="computeroutput">T</code> must be a pointer type. </p></td> </tr> <tr> <td><p><span class="term">Requires:</span></p></td> <td><p><code class="computeroutput">Concept</code> must contain typeid_<code class="computeroutput"></code><Tag>.</p></td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td> <a class="link" href="../bad_any_cast.html" title="Class bad_any_cast">bad_any_cast</a> if <code class="computeroutput">arg</code> doesn't contain an object of type <code class="computeroutput">T</code> and we're casting to a value or reference. </td> </tr> </tbody> </table></div> </div> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2011-2013 Steven Watanabe<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>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="constructible.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../boost_typeerasure/reference.html#header.boost.type_erasure.any_cast_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="dynamic_binding.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>