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           <h2 align="center">Header &lt;boost/python/def_visitor.hpp&gt;</h2>
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     <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-synopsis">Class <code>def_visitor</code>
         synopsis</a></dd>
       <dd> <a href="#def_visitor-requirements">Class <code>def_visitor</code>
         requirements</a></dd>
     </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 <tt>DerivedVisitor</tt>, 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. Its 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-synopsis" id="def_visitor-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="def_visitor-requirements"></a><code>def_visitor </code>requirements</h3>


 <p>The <span class="pre">client supplied class </span><span class="pre"></span><tt class="literal"><span class="pre">DerivedVisitor</span></tt>
   template parameter is expected to:
 <ul>
   <li>be privately derived from def_visitor</li>
   <li>grant friend access to class def_visitor_access</li>
   <li>define either or both visit member functions listed in the table below:</li>
 </ul>


 <table border class="table">
   <tr>
     <td width="181" nowrap><b>Expression</b></td>
     <td width="85"><b>Return Type</b></td>
     <td width="330"><b>Requirements</b></td>
     <td width="259"><b>Effects</b></td>
   </tr>
   <tr>
     <td nowrap>visitor.visit(cls)</td>
     <td>void</td>
     <td>cls is an instance of a <a href="class.html">class_</a>&nbsp; being wrapped
       to Python. visitor is a def_visitor derived class.</td>
     <td>A call to cls.def(visitor) forwards to this member function.</td>
   </tr>
   <tr>
     <td nowrap>visitor.visit(cls, name, options)</td>
     <td>void</td>
     <td>cls is a class_ instance, name is a C string. visitor is a def_visitor
       derived class. options is a context specific optional argument.</td>
     <td>A call to cls.def(name, visitor) or cls.def(name, visitor, options) forwards
       to this member function. </td>
   </tr>
 </table>

     <h2><a name="examples"></a>Example</h2>


 <pre>class X {/*...*/};<br>
 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(X&amp; self);
     static void bar(X&amp; self);
 };

 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. </i> Distributed under the Boost
    Software License, Version 1.0. (See accompanying
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
	<meta name="generator" content="Microsoft FrontPage 5.0">
	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
	<link rel="stylesheet" type="text/css" href="../boost.css">

	<title>Boost.Python - <boost/python/def_visitor.hpp></title>

	<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
	"header">
	<tr>
	<td valign="top" width="300">
	<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
	"C++ Boost" src="../../../../boost.png" border="0"></a></h3>

	<td valign="top">
	<h1 align="center"><a href="../index.html"><font size="7">Boost.Python</font></a></h1>

	<h2 align="center">Header <boost/python/def_visitor.hpp></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-synopsis">Class <code>def_visitor</code>
	synopsis</a></dd>
	<dd> <a href="#def_visitor-requirements">Class <code>def_visitor</code>
	requirements</a></dd>
	</dl>
	<dt><a href="#examples">Example</a>
	</dl>
	<hr>

	<h2><a name="introduction"></a>Introduction</h2>


	<p><code><boost/python/def_visitor.hpp></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<T> </code>class template,
	which is parameterized on the derived type <tt>DerivedVisitor</tt>, 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<DerivedVisitor></code></h3>


	<p>The class def_visitor is a base class paramaterized by its derived class. The
	def_visitor class is a protocol class. Its 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,  is passed
	on as an argument to the <a href="class.html">class_</a> def member function.
	<h4>
	<a name="def_visitor-synopsis" id="def_visitor-synopsis"></a>Class <code>def_visitor </code>synopsis</h4>
	<pre>namespace boost { namespace python {

	template <class DerivedVisitor>
	class def_visitor {};
	}</pre>
	<h3><a name="def_visitor-requirements"></a><code>def_visitor </code>requirements</h3>


	<p>The <span class="pre">client supplied class </span><span class="pre"></span><tt class="literal"><span class="pre">DerivedVisitor</span></tt>
	template parameter is expected to:
	<ul>
	<li>be privately derived from def_visitor</li>
	<li>grant friend access to class def_visitor_access</li>
	<li>define either or both visit member functions listed in the table below:</li>
	</ul>


	<table border class="table">
	<tr>
	<td width="181" nowrap><b>Expression</b></td>
	<td width="85"><b>Return Type</b></td>
	<td width="330"><b>Requirements</b></td>
	<td width="259"><b>Effects</b></td>
	</tr>
	<tr>
	<td nowrap>visitor.visit(cls)</td>
	<td>void</td>
	<td>cls is an instance of a <a href="class.html">class_</a>  being wrapped
	to Python. visitor is a def_visitor derived class.</td>
	<td>A call to cls.def(visitor) forwards to this member function.</td>
	</tr>
	<tr>
	<td nowrap>visitor.visit(cls, name, options)</td>
	<td>void</td>
	<td>cls is a class_ instance, name is a C string. visitor is a def_visitor
	derived class. options is a context specific optional argument.</td>
	<td>A call to cls.def(name, visitor) or cls.def(name, visitor, options) forwards
	to this member function. </td>
	</tr>
	</table>

	<h2><a name="examples"></a>Example</h2>


	<pre>class X {/.../};<br>
	class my_def_visitor : boost::python::def_visitor<my_def_visitor>
	{
	friend class def_visitor_access;

	template <class classT>
	void visit(classT& c) const
	{
	c
	.def("foo", &my_def_visitor::foo)
	.def("bar", &my_def_visitor::bar)
	;
	}

	static void foo(X& self);
	static void bar(X& self);
	};

	BOOST_PYTHON_MODULE(my_ext)
	{
	class_<X>("X")
	.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>© Copyright Joel de Guzman 2003. </i> Distributed under the Boost
	Software License, Version 1.0. (See accompanying
	file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)