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enable_shared_from_this documentation added.

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[SVN r16319]
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Peter Dimov
2002-11-19 14:22:58 +00:00
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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>&lt;boost/enable_shared_from_this.hpp&gt;</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&lt;T&gt;</STRONG> defines two member functions
called <STRONG>shared_from_this</STRONG> that return a <STRONG>shared_ptr&lt;T&gt;</STRONG>
and <STRONG>shared_ptr&lt;T const&gt;</STRONG>, depending on constness, to <STRONG>this</STRONG>.</P>
<h3><a name="Example">Example</a></h3>
<pre>
class Y: public enable_shared_from_this&lt;Y&gt;
{
public:
shared_ptr&lt;Y&gt; f()
{
return shared_from_this();
}
}
int main()
{
shared_ptr&lt;Y&gt; p(new Y);
shared_ptr&lt;Y&gt; q = p-&gt;f();
assert(p == q);
assert(!(p &lt; q || q &lt; p)); // p and q must share ownership
}
</pre>
<h3><a name="Synopsis">Synopsis</a></h3>
<pre>
namespace boost
{
template&lt;class T&gt; class enable_shared_from_this
{
public:
shared_ptr&lt;T&gt; shared_from_this();
shared_ptr&lt;T const&gt; shared_from_this() const;
}
}
</pre>
<h4>template&lt;class T&gt; shared_ptr&lt;T&gt;
enable_shared_from_this&lt;T&gt;::shared_from_this();</h4>
<h4>template&lt;class T&gt; shared_ptr&lt;T const&gt;
enable_shared_from_this&lt;T&gt;::shared_from_this() const;</h4>
<blockquote>
<p>
<b>Requires:</b> <STRONG>enable_shared_from_this&lt;T&gt;</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 have
existed at least one <STRONG>shared_ptr</STRONG> instance <STRONG>p</STRONG> pointing
to <STRONG>t</STRONG>.
</p>
<p>
<b>Returns:</b> A <b>shared_ptr&lt;T&gt;</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 <20> 2002 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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