boost_1_45_0/libs/python/doc/v2/call_method.html - nest-learning-thermostat/5.0/boost - Git at Google

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           <h1 align="center"><a href="../index.html">Boost.Python</a></h1>

           <h2 align="center">Header &lt;call_method.hpp&gt;</h2>
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     <hr>

     <h2>Contents</h2>

     <dl class="page-index">
       <dt><a href="#introduction">Introduction</a></dt>

       <dt><a href="#functions">Functions</a></dt>

       <dd>
         <dl class="page-index">
           <dt><a href="#call_method-spec">call_method</a></dt>
         </dl>
       </dd>

       <dt><a href="#examples">Example(s)</a></dt>
     </dl>
     <hr>

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

     <p><code>&lt;boost/python/call_method.hpp&gt;</code> defines the <a href=
     "#call_method-spec"><code>call_method</code></a> family of overloaded
     function templates, used to invoke callable attributes of Python objects
     from C++.</p>

     <h2><a name="functions"></a>Functions</h2>
 <pre>
 <a name=
 "call_method-spec">template &lt;class R, class A1, class A2, ... class A<i>n</i>&gt;</a>
 R call_method(PyObject* self, char const* method, A1 const&amp;, A2 const&amp;, ... A<i>n</i> const&amp;)
 </pre>

     <dl class="function-semantics">
       <dt><b>Requires:</b> <code>R</code> is a pointer type, reference type,
       or a complete type with an accessible copy constructor</dt>

       <dt><b>Effects:</b> Invokes
       <code>self.<i>method</i>(a1,&nbsp;a2,&nbsp;...a<i>n</i>)</code> in
       Python, where <code>a1</code>...<code>a<i>n</i></code> are the
       arguments to <code>call_method()</code>, converted to Python objects.
       For a complete semantic description, see <a href="callbacks.html">this
       page</a>.</dt>

       <dt><b>Returns:</b> The result of the Python call, converted to the C++
       type <code>R</code>.</dt>

       <dt><b>Rationale:</b> <code>call_method</code> is critical to
       implementing C++ virtual functions which are overridable in Python, as
       shown by the example below.</dt>
     </dl>

     <h2><a name="examples"></a>Example(s)</h2>
     The following C++ illustrates the use of <code>call_method</code> in
     wrapping a class with a virtual function that can be overridden in
     Python:

     <h3>C++ Module Definition</h3>
 <pre>
 #include &lt;boost/python/module.hpp&gt;
 #include &lt;boost/python/class.hpp&gt;
 #include &lt;boost/utility.hpp&gt;
 #include &lt;cstring&gt;

 // class to be wrapped
 class Base
 {
  public:
    virtual char const* class_name() const { return "Base"; }
    virtual ~Base();
 };

 bool is_base(Base* b)
 {
    return !std::strcmp(b-&gt;class_name(), "Base");
 }

 // Wrapper code begins here
 using namespace boost::python;

 // Callback class
 class Base_callback : public Base
 {
  public:
    Base_callback(PyObject* self) : m_self(self) {}

    char const* class_name() const { return <b>call_method</b>&lt;char const*&gt;(m_self, "class_name"); }
    char const* Base_name() const { return Base::class_name(); }
  private:
    PyObject* const m_self;
 };

 using namespace boost::python;
 BOOST_PYTHON_MODULE(my_module)
 {
     def("is_base", is_base);

     class_&lt;Base,Base_callback, noncopyable&gt;("Base")
         .def("class_name", &amp;Base_callback::Base_name)
         ;

 }
 </pre>

     <h3>Python Code</h3>
 <pre>
 &gt;&gt;&gt; from my_module import *
 &gt;&gt;&gt; class Derived(Base):
 ...    def __init__(self):
 ...       Base.__init__(self)
 ...    def class_name(self):
 ...       return self.__class__.__name__
 ...
 &gt;&gt;&gt; is_base(Base()) # calls the class_name() method from C++
 1
 &gt;&gt;&gt; is_base(Derived())
 0
 </pre>

     <p>Revised
     <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
   13 November, 2002
   <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
     </p>

     <p><i>&copy; Copyright <a href=
     "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p>
   </body>
 </html>
	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

	<!-- Copyright David Abrahams 2006. 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) -->
	<html>
	<head>
	<meta name="generator" content=
	"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
	<link rel="stylesheet" type="text/css" href="../boost.css">

	<title>Boost.Python - <call_method.hpp></title>
	</head>

	<body link="#0000ff" vlink="#800080">
	<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>

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

	<h2 align="center">Header <call_method.hpp></h2>
	</td>
	</tr>
	</table>
	<hr>

	<h2>Contents</h2>

	<dl class="page-index">
	<dt><a href="#introduction">Introduction</a></dt>

	<dt><a href="#functions">Functions</a></dt>

	<dd>
	<dl class="page-index">
	<dt><a href="#call_method-spec">call_method</a></dt>
	</dl>
	</dd>

	<dt><a href="#examples">Example(s)</a></dt>
	</dl>
	<hr>

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

	<p><code><boost/python/call_method.hpp></code> defines the <a href=
	"#call_method-spec"><code>call_method</code></a> family of overloaded
	function templates, used to invoke callable attributes of Python objects
	from C++.</p>

	<h2><a name="functions"></a>Functions</h2>
	<pre>
	<a name=
	"call_method-spec">template <class R, class A1, class A2, ... class A<i>n</i>></a>
	R call_method(PyObject* self, char const* method, A1 const&, A2 const&, ... A<i>n</i> const&)
	</pre>

	<dl class="function-semantics">
	<dt><b>Requires:</b> <code>R</code> is a pointer type, reference type,
	or a complete type with an accessible copy constructor</dt>

	<dt><b>Effects:</b> Invokes
	<code>self.<i>method</i>(a1, a2, ...a<i>n</i>)</code> in
	Python, where <code>a1</code>...<code>a<i>n</i></code> are the
	arguments to <code>call_method()</code>, converted to Python objects.
	For a complete semantic description, see <a href="callbacks.html">this
	page</a>.</dt>

	<dt><b>Returns:</b> The result of the Python call, converted to the C++
	type <code>R</code>.</dt>

	<dt><b>Rationale:</b> <code>call_method</code> is critical to
	implementing C++ virtual functions which are overridable in Python, as
	shown by the example below.</dt>
	</dl>

	<h2><a name="examples"></a>Example(s)</h2>
	The following C++ illustrates the use of <code>call_method</code> in
	wrapping a class with a virtual function that can be overridden in
	Python:

	<h3>C++ Module Definition</h3>
	<pre>
	#include <boost/python/module.hpp>
	#include <boost/python/class.hpp>
	#include <boost/utility.hpp>
	#include <cstring>

	// class to be wrapped
	class Base
	{
	public:
	virtual char const* class_name() const { return "Base"; }
	virtual ~Base();
	};

	bool is_base(Base* b)
	{
	return !std::strcmp(b->class_name(), "Base");
	}

	// Wrapper code begins here
	using namespace boost::python;

	// Callback class
	class Base_callback : public Base
	{
	public:
	Base_callback(PyObject* self) : m_self(self) {}

	char const* class_name() const { return <b>call_method</b><char const*>(m_self, "class_name"); }
	char const* Base_name() const { return Base::class_name(); }
	private:
	PyObject* const m_self;
	};

	using namespace boost::python;
	BOOST_PYTHON_MODULE(my_module)
	{
	def("is_base", is_base);

	class_<Base,Base_callback, noncopyable>("Base")
	.def("class_name", &Base_callback::Base_name)
	;

	}
	</pre>

	<h3>Python Code</h3>
	<pre>
	>>> from my_module import *
	>>> class Derived(Base):
	... def __init__(self):
	... Base.__init__(self)
	... def class_name(self):
	... return self.__class__.__name__
	...
	>>> is_base(Base()) # calls the class_name() method from C++
	1
	>>> is_base(Derived())
	0
	</pre>

	<p>Revised
	<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
	13 November, 2002
	<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
	</p>

	<p><i>© Copyright <a href=
	"http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p>
	</body>
	</html>