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Initial commit of def_visitor doc

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<title>Boost.Python - &lt;boost/python/def_visitor.hpp&gt;</title>
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<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
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<h1 align="center"><a href="../index.html"><font size="7">Boost.Python</font></a></h1>
<h2 align="center">Header &lt;boost/python/def_visitor.hpp&gt;</h2>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a>
<dt><a href="#classes">Classes</a>
<dd>
<dl class="page-index">
<dt><a href="#def_visitor-spec">Class <code>def_visitor</code></a><dd>
<a href="#def_visitor-spec-synopsis">Class <code>def_visitor</code> synopsis</a>
</dd>
</dl>
<dd>
<dl class="page-index">
<dt><a href="#my_def_visitor-spec">Class <code>my_def_visitor</code></a>
<dd>
<dl class="page-index">
<dt><a href="#my_def_visitor-spec-synopsis">Class my_def_visitor synopsis</a>
<dt><a href="#my_def_visitor-spec-observers">Class my_def_visitor observer functions</a>
</dl>
</dl>
<dt><a href="#examples">Example</a>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p><code>&lt;boost/python/def_visitor.hpp&gt;</code> provides a generic visitation
interface through which the <a href="class.html">class_</a> <b>def</b>
member functionality can be extended non-intrusively to avoid cluttering the
<a href="class.html">class_</a> interface. It declares the <code>def_visitor&lt;T&gt;
</code>class template, which is parameterized on the derived type T, which
provides the actual <b>def</b> functionality through its <b>visit</b> member
functions.<h2><a name="classes"></a>Classes</h2>
<h3><a name="def_visitor-spec"></a>Class template <code>def_visitor&lt;DerivedVisitor&gt;</code></h3>
<p>The class def_visitor is a base class paramaterized by its derived class.
The def_visitor class is a protocol class. It's derived class,
DerivedVisitor, is expected to have a member function visit. The def_visitor
class is never instantiated directly. Instead, an instance of its subclass,
DerivedVisitor,&nbsp; is passed on as an argument to the
<a href="class.html">class_</a> def member function.<h4>
<a name="def_visitor-spec-synopsis"></a>Class <code>def_visitor </code>synopsis</h4>
<pre>namespace boost { namespace python {
template &lt;class DerivedVisitor&gt;
class def_visitor {};
}</pre>
<h3><a name="my_def_visitor-spec"></a>Class <tt>my_</tt><code>def_visitor</code></h3>
<p>A prototypical derived class of def_visitor. This client supplied class
is expected to<ul>
<li>be privately derived from def_visitor</li>
<li>grant friend access to def_visitor_access</li>
<li>define either or both visit member functions.</li>
</ul>
<h4><a name="my_def_visitor-spec-synopsis"></a>Class <code>my_def_visitor </code> synopsis</h4>
<pre> class my_def_visitor : boost::python::def_visitor&lt;my_def_visitor&gt;
{
friend class def_visitor_access;
template &lt;class classT&gt;
void visit(classT&amp; c) const;
template &lt;class classT, class OptionalArgs&gt;
void visit(classT&amp; c, char const* name, OptionalArgs const&amp; options) const;
};
</pre>
<h4><a name="my_def_visitor-spec-observers"></a>Class <code>my_def_visitor </code>
observer functions</h4>
<pre>template &lt;class classT&gt;
void visit(classT&amp; c) const;</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> c is an instance of a <a href="class.html">class_</a>&nbsp;
being wrapped to Python. This is a client supplied function.
<dt><b>Effects:</b> A call to c.def(visitor), where c is a class_ instance and
visitor is a def_visitor derived class forwards to this visitor's visit member
function.
<dt><b> Rationale:</b> Allows my_def_visitor to non-intrusively add functionality
to the <a href="class.html">class_</a> def member function.
</dl>
<pre>template &lt;class classT, class OptionalArgs&gt;
void visit(classT&amp; c, char const* name, OptionalArgs const&amp; options) const;</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> c is an instance of a <a href="class.html">class_</a>&nbsp;
being wrapped to Python. name is a client supplied name. This is a client
supplied function.
<dt><b>Effects:</b> A call to c.def(name, visitor) or c.def(name, visitor, options),
where c is a class_ instance and visitor is a def_visitor derived class forwards
to this visitor's visit member function.
<dt><b>Rationale:</b> Allows my_def_visitor to non-intrusively add functionality
to the <a href="class.html">class_</a> def member function.
</dl>
<h2><a name="examples"></a>Example</h2>
<pre> class my_def_visitor : boost::python::def_visitor&lt;my_def_visitor&gt;
{
friend class def_visitor_access;
template &lt;class classT&gt;
void visit(classT&amp; c) const
{
c
.def(&quot;foo&quot;, &amp;my_def_visitor::foo)
.def(&quot;bar&quot;, &amp;my_def_visitor::bar)
;
}
static void foo(object self);
static void bar(object self);
};
class X {/*...*/};
BOOST_PYTHON_MODULE(my_ext)
{
class_&lt;X&gt;(&quot;X&quot;)
.def(my_def_visitor())
;
}
</pre>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->27 August, 2003<!--webbot bot="Timestamp" endspan i-checksum="34484" -->
</p>
<p><i>&copy; Copyright Joel de Guzman 2003. All Rights Reserved.</i>