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Add weak_from_this.
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Peter Dimov
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<title>enable_shared_from_this</title>
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<h1><img height="86" alt="boost.png (6897 bytes)" src="../../boost.png"
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width="277" align="middle" border="0">enable_shared_from_this</h1>
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<h1><img height="86" alt="boost.png (6897 bytes)" src="../../boost.png"
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width="277" align="middle" border="0" />enable_shared_from_this</h1>
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<h2><a name="Purpose">Purpose</a></h2>
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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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The header <code><boost/enable_shared_from_this.hpp></code> defines
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the class template <code>enable_shared_from_this</code>. It is used as a
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base class that allows a <a href="shared_ptr.htm">shared_ptr</a> or
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a <a href="weak_ptr.htm">weak_ptr</a> to the current object to be obtained
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from within a member function.
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</p>
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<p><code>enable_shared_from_this<T></code> defines two member functions
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called <code>shared_from_this</code> that return a <code>shared_ptr<T></code>
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and <code>shared_ptr<T const></code>, depending on constness, to <code>this</code>.
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It also defines two member functions called <code>weak_from_this</code> that return
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a corresponding <code>weak_ptr</code>.
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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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<h2><a name="Example">Example</a></h2>
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<pre>
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#include <boost/enable_shared_from_this.hpp>
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@@ -41,7 +45,7 @@ int main()
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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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<h2><a name="Synopsis">Synopsis</a></h2>
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<pre>
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namespace boost
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{
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@@ -52,34 +56,55 @@ 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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weak_ptr<T> weak_from_this() noexcept;
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weak_ptr<T const> weak_from_this() const noexcept;
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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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<h4><code>template<class T> shared_ptr<T>
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enable_shared_from_this<T>::shared_from_this();</code></h4>
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<h4><code>template<class T> shared_ptr<T const>
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enable_shared_from_this<T>::shared_from_this() const;</code></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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<b>Requires:</b> <code>enable_shared_from_this<T></code> must be an
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accessible base class of <code>T</code>. <code>*this</code> must be a subobject
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of an instance <code>t</code> of type <code>T</code>.
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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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<b>Returns:</b> If a <code>shared_ptr</code> instance <code>p</code> that <em>owns</em>
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<code>t</code> exists, a <code>shared_ptr<T></code> instance <code>r</code> that shares
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ownership with <code>p</code>.
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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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<b>Postconditions:</b> <code>r.get() == this</code>.
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</p>
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<p>
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<b>Throws:</b> <code>bad_weak_ptr</code> when no <code>shared_ptr</code> <em>owns</em> <code>*this</code>.
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</p>
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</blockquote>
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<p>$Date$</p>
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<h4><code>template<class T> weak_ptr<T>
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enable_shared_from_this<T>::weak_from_this() noexcept;</code></h4>
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<h4><code>template<class T> weak_ptr<T const>
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enable_shared_from_this<T>::weak_from_this() const noexcept;</code></h4>
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<blockquote>
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<p>
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<b>Requires:</b> <code>enable_shared_from_this<T></code> must be an
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accessible base class of <code>T</code>. <code>*this</code> must be a subobject
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of an instance <code>t</code> of type <code>T</code>.
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</p>
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<p>
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<b>Returns:</b> If a <code>shared_ptr</code> instance <code>p</code> that <em>owns</em>
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<code>t</code> exists or has existed in the past, a <code>weak_ptr<T></code> instance
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<code>r</code> that shares ownership with <code>p</code>. Otherwise, an empty <code>weak_ptr</code>.
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</p>
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</blockquote>
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<hr />
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<p>
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<small>Copyright © 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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<small>Copyright © 2002, 2003, 2015 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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</body>
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</html>
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