1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> 5<title>polymorphic_pointer_downcast example</title> 6<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../conversion.html" title="Chapter 11. The Conversion Library 1.6"> 10<link rel="prev" href="_polymorphic_downcast__example.html" title="polymorphic_downcast example"> 11<link rel="next" href="history.html" title="History"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> 16<td align="center"><a href="../../../index.html">Home</a></td> 17<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="_polymorphic_downcast__example.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../conversion.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="history.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="section"> 27<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 28<a name="conversion._polymorphic_pointer_downcast__example"></a><a class="link" href="_polymorphic_pointer_downcast__example.html" title="polymorphic_pointer_downcast example"><code class="computeroutput">polymorphic_pointer_downcast</code> 29 example</a> 30</h2></div></div></div> 31<pre class="programlisting">#include <boost/polymorphic_pointer_cast.hpp> 32 33class Fruit { public: virtual ~Fruit(){} }; 34class Banana : public Fruit {}; 35 36// use one of these: 37 38typedef Fruit* FruitPtr; 39typedef std::shared_ptr<Fruit> FruitPtr; 40typedef boost::shared_ptr<Fruit> FruitPtr; 41typedef boost::intrusive_ptr<Fruit> FruitPtr; 42 43void f(FruitPtr fruit) { 44 // ... logic which leads us to believe it is a banana 45 auto banana = boost::polymorphic_pointer_downcast<Banana>(fruit); 46 ... 47} 48</pre> 49</div> 50<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 51<td align="left"></td> 52<td align="right"><div class="copyright-footer">Copyright © 2001 Beman Dawes<br>Copyright © 2014-2019 Antony Polukhin<p> 53 Distributed under the Boost Software License, Version 1.0. (See accompanying 54 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>) 55 </p> 56</div></td> 57</tr></table> 58<hr> 59<div class="spirit-nav"> 60<a accesskey="p" href="_polymorphic_downcast__example.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../conversion.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="history.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 61</div> 62</body> 63</html> 64
