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name="boost.signals2.deconstruct"></a><div class="titlepage"></div> <div class="refnamediv"> <h2><span class="refentrytitle">Function deconstruct</span></h2> <p>boost::signals2::deconstruct — Create a <code class="computeroutput">shared_ptr</code> with support for post-constructors and pre-destructors.</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="../../signals2/reference.html#header.boost.signals2.deconstruct_hpp" title="Header <boost/signals2/deconstruct.hpp>">boost/signals2/deconstruct.hpp</a>> </span> <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> <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> <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> <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> <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> <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> <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><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> <div class="refsect1"> <a name="idm45555131836656"></a><h2>Description</h2> <p>Creates an object and its owning <code class="computeroutput">shared_ptr<T></code> (wrapped inside a <code class="computeroutput"><a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a></code>) using only a single allocation, in a manner similar to that of <code class="computeroutput">boost::make_shared()</code>. In addition, <code class="computeroutput">deconstruct</code> supports postconstructors and predestructors. The returned <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> in order to provide the user with an opportunity to pass arguments to a postconstructor, while insuring the postconstructor is run before the wrapped <code class="computeroutput">shared_ptr</code> is accessible. </p> <p> In order to use <code class="computeroutput">deconstruct</code> you must define a postconstructor for your class. More specifically, you must define an <code class="computeroutput">adl_postconstruct</code> function which can be found via argument-dependent lookup. Typically, this means defining an <code class="computeroutput">adl_postconstruct</code> function in the same namespace as its associated class. See the reference for <code class="computeroutput"><a class="link" href="postconstructor_invoker.html" title="Class postconstructor_invoker">postconstructor_invoker</a></code> for a specification of what arguments are passed to the <code class="computeroutput">adl_postconstruct</code> call. </p> <p> Optionally, you may define a predestructor for your class. This is done by defining an <code class="computeroutput">adl_predestruct</code> function which may be found by argument-dependent lookup. The deleter of the <code class="computeroutput">shared_ptr</code> created by <code class="computeroutput">deconstruct</code> will make an unqualified call to <code class="computeroutput">adl_predestruct</code> with a single argument: a pointer to the object which is about to be deleted. As a convenience, the pointer will always be cast to point to a non-const type before being passed to <code class="computeroutput">adl_predestruct</code>. If no user-defined <code class="computeroutput">adl_predestruct</code> function is found via argument-dependent lookup, a default function (which does nothing) will be used. After <code class="computeroutput">adl_predestruct</code> is called, the deleter will delete the object with <code class="computeroutput">checked_delete</code>. </p> <p> Any arguments passed to a <code class="computeroutput">deconstruct()</code> call are forwarded to the matching constructor of the template type <code class="computeroutput">T</code>. Arguments may also be passed to the class' associated <code class="computeroutput">adl_postconstruct</code> function by using the <code class="computeroutput"><a class="link" href="postconstructor_invoker.html#idm45507042235504-bb">postconstructor_invoker::postconstruct()</a></code> methods. </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">Notes:</span></p></td> <td> <p>If your compiler supports the C++11 features of rvalue references and variadic templates, then <code class="computeroutput">deconstruct</code> will perform perfect forwarding of arguments to the <code class="computeroutput">T</code> constructor, using a prototype of: </p> <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> <p>Otherwise, argument forwarding is performed via const references, as specified in the synopsis. In order to pass non-const references to a constructor, you will need to wrap them in reference wrappers using boost::ref. </p> <p>You may give all the <code class="computeroutput">deconstruct</code> overloads access to your class' private and protected constructors by declaring <a class="link" href="deconstruct_access.html" title="Class deconstruct_access">deconstruct_access</a> a friend. Using private constructors in conjunction with <a class="link" href="deconstruct_access.html" title="Class deconstruct_access">deconstruct_access</a> can be useful to ensure your objects are only created by <code class="computeroutput">deconstruct</code>, and thus their postconstructors or predestructors will always be called. </p> </td> </tr> <tr> <td><p><span class="term">Returns:</span></p></td> <td><p>A <code class="computeroutput">postconstructor_invoker<T></code> owning a newly allocated object of type <code class="computeroutput">T</code>.</p></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 © 2001-2004 Douglas Gregor<br>Copyright © 2007-2009 Frank Mori Hess<p>Distributed under the Boost Software License, Version 1.0. (See accompanying file <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> </div></td> </tr></table> <hr> <div class="spirit-nav"> <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> </div> </body> </html>