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<title>Boost: enable_shared_from_this.hpp documentation</title>
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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>
class Y: public enable_shared_from_this<Y>
{
public:
shared_ptr<Y> f()
{
return shared_from_this();
}
}
int main()
{
shared_ptr<Y> p(new Y);
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. Permission to copy, use, modify, sell
and distribute this document is granted provided this copyright notice appears
in all copies. This document is provided "as is" without express or implied
warranty, and with no claim as to its suitability for any purpose.</small></p>
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