boost-react-native-bundle

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">    <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  13 November, 2002  </p> <p><i>© Copyright <a href= "http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p> </body> </html>