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<title>Function deconstruct</title>
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<div class="refentry">
<a 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="idp205202056"></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#idp93725592-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++0x 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>
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<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>
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