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=UTF-8"> 5<title>Function deconstruct</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="../../signals2/reference.html#header.boost.signals2.deconstruct_hpp" title="Header <boost/signals2/deconstruct.hpp>"> 10<link rel="prev" href="scoped_connection.html" title="Class scoped_connection"> 11<link rel="next" href="deconstruct_access.html" title="Class deconstruct_access"> 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" 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name="boost.signals2.deconstruct"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Function deconstruct</span></h2> 30<p>boost::signals2::deconstruct — Create a <code class="computeroutput">shared_ptr</code> with support for post-constructors and pre-destructors.</p> 31</div> 32<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 33<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="../../signals2/reference.html#header.boost.signals2.deconstruct_hpp" title="Header <boost/signals2/deconstruct.hpp>">boost/signals2/deconstruct.hpp</a>> 34 35</span> 36<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">deconstruct</span><span class="special">(</span><span class="special">)</span><span class="special">;</span> 37<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">,</span> <span class="keyword">typename</span> A1<span class="special">></span> 38 <a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">deconstruct</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">A1</span> <span class="special">&</span> arg1<span class="special">)</span><span class="special">;</span> 39<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">,</span> <span class="keyword">typename</span> A1<span class="special">,</span> <span class="keyword">typename</span> A2<span class="special">></span> 40 <a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">deconstruct</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">A1</span> <span class="special">&</span> arg1<span class="special">,</span> <span class="keyword">const</span> <span class="identifier">A2</span> <span class="special">&</span> arg2<span class="special">)</span><span class="special">;</span> 41<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">,</span> <span class="keyword">typename</span> A1<span class="special">,</span> <span class="keyword">typename</span> A2, ...<span class="special">,</span> <span class="keyword">typename</span> AN<span class="special">></span> 42 <a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a><span class="special"><</span><span class="identifier">T</span><span class="special">></span> 43 <span class="identifier">deconstruct</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">A1</span> <span class="special">&</span> arg1<span class="special">,</span> <span class="keyword">const</span> <span class="identifier">A2</span> <span class="special">&</span> arg2<span class="special">,</span> <span class="special">...</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">AN</span> <span class="special">&</span> argN<span class="special">)</span><span class="special">;</span></pre></div> 44<div class="refsect1"> 45<a name="id-1.3.36.6.4.3.4"></a><h2>Description</h2> 46<p>Creates an object and its owning <code class="computeroutput">shared_ptr<T></code> 47 (wrapped inside a <code class="computeroutput"><a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a></code>) 48 using only a single allocation, 49 in a manner similar 50 to that of <code class="computeroutput">boost::make_shared()</code>. In addition, <code class="computeroutput">deconstruct</code> 51 supports postconstructors and predestructors. The returned 52 <code class="computeroutput">shared_ptr</code> is wrapped inside a <code class="computeroutput"><a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a></code> 53 in order to provide the user with an opportunity to pass arguments to a postconstructor, 54 while insuring the postconstructor is run before the wrapped 55 <code class="computeroutput">shared_ptr</code> is accessible. 56 </p> 57<p> 58 In order to use <code class="computeroutput">deconstruct</code> you must define a postconstructor for your class. 59 More specifically, you must define 60 an <code class="computeroutput">adl_postconstruct</code> function which can be found via argument-dependent 61 lookup. Typically, this means defining an <code class="computeroutput">adl_postconstruct</code> function 62 in the same namespace as its associated class. See the reference for 63 <code class="computeroutput"><a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a></code> 64 for a specification of what arguments are passed to the <code class="computeroutput">adl_postconstruct</code> 65 call. 66 </p> 67<p> 68 Optionally, you may define a predestructor for your class. This is done by 69 defining an <code class="computeroutput">adl_predestruct</code> function which may be found 70 by argument-dependent lookup. The deleter of the <code class="computeroutput">shared_ptr</code> 71 created by <code class="computeroutput">deconstruct</code> will make an unqualified call to 72 <code class="computeroutput">adl_predestruct</code> with a single 73 argument: a pointer to the object which is about to be deleted. 74 As a convenience, the pointer will always be cast to point to a non-const type 75 before being passed to <code class="computeroutput">adl_predestruct</code>. 76 If no user-defined <code class="computeroutput">adl_predestruct</code> function is found via 77 argument-dependent lookup, a default function (which does nothing) will 78 be used. After <code class="computeroutput">adl_predestruct</code> is called, the deleter 79 will delete the object with 80 <code class="computeroutput">checked_delete</code>. 81 </p> 82<p> 83 Any arguments passed to a 84 <code class="computeroutput">deconstruct()</code> call are forwarded to the matching constructor of the 85 template type 86 <code class="computeroutput">T</code>. Arguments may also be passed to the class' associated 87 <code class="computeroutput">adl_postconstruct</code> function by using the 88 <code class="computeroutput"><a class="link" href="postconstructor_invoker.html#id-1_3_36_6_3_3_1_3_1_2-bb">postconstructor_invoker::postconstruct()</a></code> methods. 89 </p> 90<div class="variablelist"><table border="0" class="variablelist compact"> 91<colgroup> 92<col align="left" valign="top"> 93<col> 94</colgroup> 95<tbody> 96<tr> 97<td><p><span class="term">Notes:</span></p></td> 98<td> 99<p>If your compiler supports the C++11 features of rvalue references 100 and variadic templates, then <code class="computeroutput">deconstruct</code> will perform perfect 101 forwarding of arguments to the <code class="computeroutput">T</code> constructor, using 102 a prototype of: 103 </p> 104<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">typename</span><span class="special">...</span> <span class="identifier">Args</span> <span class="special">></span> <span class="identifier">postconstructor_invoker</span><span class="special"><</span> <span class="identifier">T</span> <span class="special">></span> <span class="identifier">deconstruct</span><span class="special">(</span> <span class="identifier">Args</span> <span class="special">&&</span> <span class="special">...</span> <span class="identifier">args</span> <span class="special">)</span><span class="special">;</span></pre> 105<p>Otherwise, argument forwarding is performed via const references, as specified in 106 the synopsis. In order to pass non-const references to a constructor, you will need 107 to wrap them in reference wrappers using boost::ref. 108 </p> 109<p>You may give all the <code class="computeroutput">deconstruct</code> overloads access to your class' 110 private and protected constructors by 111 declaring <a class="link" href="deconstruct_access.html" title="Class deconstruct_access">deconstruct_access</a> a friend. Using private 112 constructors in conjunction with <a class="link" href="deconstruct_access.html" title="Class deconstruct_access">deconstruct_access</a> 113 can be useful to 114 ensure your objects are only created by <code class="computeroutput">deconstruct</code>, and thus 115 their postconstructors or predestructors will always be called. 116 </p> 117</td> 118</tr> 119<tr> 120<td><p><span class="term">Returns:</span></p></td> 121<td><p>A <code class="computeroutput">postconstructor_invoker<T></code> owning a newly allocated object of 122 type <code class="computeroutput">T</code>.</p></td> 123</tr> 124</tbody> 125</table></div> 126</div> 127</div> 128<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 129<td align="left"></td> 130<td align="right"><div class="copyright-footer">Copyright © 2001-2004 Douglas Gregor<br>Copyright © 2007-2009 Frank Mori Hess<p>Distributed under the Boost 131 Software License, Version 1.0. (See accompanying file 132 <code class="filename">LICENSE_1_0.txt</code> 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> 133</div></td> 134</tr></table> 135<hr> 136<div class="spirit-nav"> 137<a accesskey="p" href="scoped_connection.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../signals2/reference.html#header.boost.signals2.deconstruct_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="deconstruct_access.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 138</div> 139</body> 140</html> 141
