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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<title>Boost: enable_shared_from_this.hpp documentation</title>
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<body bgcolor="white" style="MARGIN-LEFT: 5%; MARGIN-RIGHT: 5%">
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<table border="0" width="100%">
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<tr>
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<td width="277"><A href="../../index.htm"> <img src="../../boost.png" alt="boost.png (6897 bytes)" width="277" height="86" border="0"></A>
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</td>
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<td align="center">
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<h1>enable_shared_from_this.hpp</h1>
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<tr>
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<td colspan="2" height="64"> </td>
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</table>
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<h3><a name="Purpose">Purpose</a></h3>
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<p>
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The header <STRONG><boost/enable_shared_from_this.hpp></STRONG> defines
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the class template <STRONG>enable_shared_from_this</STRONG>. It is used as a
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base class that allows a <A href="shared_ptr.htm">shared_ptr</A> to the current
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object to be obtained from within a member function.
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</p>
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<P><STRONG>enable_shared_from_this<T></STRONG> defines two member functions
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called <STRONG>shared_from_this</STRONG> that return a <STRONG>shared_ptr<T></STRONG>
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and <STRONG>shared_ptr<T const></STRONG>, depending on constness, to <STRONG>this</STRONG>.</P>
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<h3><a name="Example">Example</a></h3>
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<pre>
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class Y: public enable_shared_from_this<Y>
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{
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public:
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shared_ptr<Y> f()
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{
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return shared_from_this();
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}
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}
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int main()
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{
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shared_ptr<Y> p(new Y);
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shared_ptr<Y> q = p->f();
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assert(p == q);
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assert(!(p < q || q < p)); // p and q must share ownership
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}
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</pre>
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<h3><a name="Synopsis">Synopsis</a></h3>
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<pre>
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namespace boost
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{
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template<class T> class enable_shared_from_this
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{
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public:
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shared_ptr<T> shared_from_this();
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shared_ptr<T const> shared_from_this() const;
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}
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}
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</pre>
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<h4>template<class T> shared_ptr<T>
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enable_shared_from_this<T>::shared_from_this();</h4>
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<h4>template<class T> shared_ptr<T const>
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enable_shared_from_this<T>::shared_from_this() const;</h4>
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<blockquote>
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<p>
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<b>Requires:</b> <STRONG>enable_shared_from_this<T></STRONG> must be an
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accessible base class of <b>T</b>. <STRONG>*this</STRONG> must be a subobject
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of an instance <STRONG>t</STRONG> of type <STRONG>T</STRONG> . There must exist
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at least one <STRONG>shared_ptr</STRONG> instance <STRONG>p</STRONG> that <EM>owns</EM>
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<STRONG>t</STRONG>.
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</p>
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<p>
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<b>Returns:</b> A <b>shared_ptr<T></b> instance <b>r</b> that shares
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ownership with <b>p</b>.
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</p>
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<p>
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<b>Postconditions:</b> <tt>r.get() == this</tt>.
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</p>
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</blockquote>
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<p>
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<br>
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<small>Copyright <20> 2002, 2003 by Peter Dimov. Distributed under the Boost Software License, Version
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1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A> or
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copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>.</small></p>
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