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| <h1>enable_shared_from_this.hpp</h1> |
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| <h3><a name="Purpose">Purpose</a></h3> |
| <p> |
| The header <STRONG><boost/enable_shared_from_this.hpp></STRONG> defines |
| the class template <STRONG>enable_shared_from_this</STRONG>. It is used as a |
| base class that allows a <A href="shared_ptr.htm">shared_ptr</A> to the current |
| object to be obtained from within a member function. |
| </p> |
| <P><STRONG>enable_shared_from_this<T></STRONG> defines two member functions |
| called <STRONG>shared_from_this</STRONG> that return a <STRONG>shared_ptr<T></STRONG> |
| and <STRONG>shared_ptr<T const></STRONG>, depending on constness, to <STRONG>this</STRONG>.</P> |
| <h3><a name="Example">Example</a></h3> |
| <pre> |
| #include <boost/enable_shared_from_this.hpp> |
| #include <boost/shared_ptr.hpp> |
| #include <cassert> |
| |
| class Y: public boost::enable_shared_from_this<Y> |
| { |
| public: |
| |
| boost::shared_ptr<Y> f() |
| { |
| return shared_from_this(); |
| } |
| }; |
| |
| int main() |
| { |
| boost::shared_ptr<Y> p(new Y); |
| boost::shared_ptr<Y> q = p->f(); |
| assert(p == q); |
| assert(!(p < q || q < p)); // p and q must share ownership |
| } |
| </pre> |
| <h3><a name="Synopsis">Synopsis</a></h3> |
| <pre> |
| namespace boost |
| { |
| |
| template<class T> class enable_shared_from_this |
| { |
| public: |
| |
| shared_ptr<T> shared_from_this(); |
| shared_ptr<T const> shared_from_this() const; |
| } |
| |
| } |
| </pre> |
| <h4>template<class T> shared_ptr<T> |
| enable_shared_from_this<T>::shared_from_this();</h4> |
| <h4>template<class T> shared_ptr<T const> |
| enable_shared_from_this<T>::shared_from_this() const;</h4> |
| <blockquote> |
| <p> |
| <b>Requires:</b> <STRONG>enable_shared_from_this<T></STRONG> must be an |
| accessible base class of <b>T</b>. <STRONG>*this</STRONG> must be a subobject |
| of an instance <STRONG>t</STRONG> of type <STRONG>T</STRONG> . There must exist |
| at least one <STRONG>shared_ptr</STRONG> instance <STRONG>p</STRONG> that <EM>owns</EM> |
| <STRONG>t</STRONG>. |
| </p> |
| <p> |
| <b>Returns:</b> A <b>shared_ptr<T></b> instance <b>r</b> that shares |
| ownership with <b>p</b>. |
| </p> |
| <p> |
| <b>Postconditions:</b> <tt>r.get() == this</tt>. |
| </p> |
| </blockquote> |
| <p> |
| <br> |
| <small>Copyright © 2002, 2003 by Peter Dimov. Distributed under the Boost Software License, Version |
| 1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A> or |
| 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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