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 - <boost/python/make_function.hpp></title> </head> <body> <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 <boost/python/make_function.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="#make_function-spec">make_function</a></dt> <dt><a href="#make_constructor-spec">make_constructor</a></dt> </dl> </dd> <dt><a href="#examples">Example</a></dt> </dl> <hr> <h2><a name="introduction"></a>Introduction</h2> <p><code><a href="#make_function-spec">make_function</a>()</code> and <code><a href="#make_constructor-spec">make_constructor</a>()</code> are the functions used internally by <code><a href= "def.html#def-spec">def</a>()</code> and <code>class_<>::<a href= "class.html#class_-spec-modifiers">def</a>()</code> to produce Python callable objects which wrap C++ functions and member functions.</p> <h2><a name="functions"></a>Functions</h2> <pre> <a name="make_function-spec">template <class F></a> <a href="object.html#object-spec">object</a> make_function(F f) template <class F, class Policies> <a href= "object.html#object-spec">object</a> make_function(F f, Policies const& policies) template <class F, class Policies, class KeywordsOrSignature> <a href= "object.html#object-spec">object</a> make_function(F f, Policies const& policies, KeywordsOrSignature const& ks) template <class F, class Policies, class Keywords, class Signature> <a href= "object.html#object-spec">object</a> make_function(F f, Policies const& policies, Keywords const& kw, Signature const& sig) </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>F</code> is a function pointer or member function pointer type. If <code>policies</code> are supplied, it must be a model of <a href="CallPolicies.html">CallPolicies</a>. If <code>kewords</code> are supplied, it must be the result of a <a href= "args.html#keyword-expression"><em>keyword-expression</em></a> specifying no more arguments than the <a href= "definitions.html#arity">arity</a> of <code>f</code>.</dt> <dt><b>Effects:</b> Creates a Python callable object which, when called from Python, converts its arguments to C++ and calls <code>f</code>. If <code>F</code> is a pointer-to-member-function type, the target object of the function call (<code>*this</code>) will be taken from the first Python argument, and subsequent Python arguments will be used as the arguments to <code>f</code>. <ul> <li> If <code>policies</code> are supplied, it will be applied to the function as described <a href= "CallPolicies.html">here</a>. <li>If <code>keywords</code> are supplied, the keywords will be applied in order to the final arguments of the resulting function. <li>If <code>Signature</code> is supplied, it should be an instance of an <a href="../../../mpl/doc/refmanual/front-extensible-sequence.html">MPL front-extensible sequence</a> representing the function's return type followed by its argument types. Pass a <code>Signature</code> when wrapping function object types whose signatures can't be deduced, or when you wish to override the types which will be passed to the wrapped function. </ul></dt> <dt><b>Returns:</b> An instance of <a href= "object.html#object-spec">object</a> which holds the new Python callable object.</dt> <dt><b>Caveats:</b> An argument of pointer type may be <code>0</code> if <code>None</code> is passed from Python. An argument type which is a constant reference may refer to a temporary which was created from the Python object for just the duration of the call to the wrapped function, for example a <code>std::vector</code> conjured up by the conversion process from a Python list. Use a non-<code>const</code> reference argument when a persistent lvalue is required. </dl> <pre> <a name="make_constructor-spec">template <class F></a> <a href="object.html#object-spec">object</a> make_constructor(F f) template <class F, class Policies> <a href= "object.html#object-spec">object</a> make_constructor(F f, Policies const& policies) template <class F, class Policies, class KeywordsOrSignature> <a href= "object.html#object-spec">object</a> make_constructor(F f, Policies const& policies, KeywordsOrSignature const& ks) template <class F, class Policies, class Keywords, class Signature> <a href= "object.html#object-spec">object</a> make_constructor(F f, Policies const& policies, Keywords const& kw, Signature const& sig) </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>F</code> is a function pointer type. If <code>policies</code> are supplied, it must be a model of <a href="CallPolicies.html">CallPolicies</a>. If <code>kewords</code> are supplied, it must be the result of a <a href= "args.html#keyword-expression"><em>keyword-expression</em></a> specifying no more arguments than the <a href= "definitions.html#arity">arity</a> of <code>f</code>.</dt> <dt><b>Effects:</b> Creates a Python callable object which, when called from Python, converts its arguments to C++ and calls <code>f</code>.</dt> <dt><b>Returns:</b> An instance of <a href= "object.html#object-spec">object</a> which holds the new Python callable object.</dt> </dl> <h2><a name="examples"></a>Example</h2> <p>C++ function exposed below returns a callable object wrapping one of two functions.</p> <pre> #include <boost/python/make_function.hpp> #include <boost/python/module.hpp> char const* foo() { return "foo"; } char const* bar() { return "bar"; } using namespace boost::python; object choose_function(bool selector) { if (selector) return boost::python::make_function(foo); else return boost::python::make_function(bar); } BOOST_PYTHON_MODULE(make_function_test) { def("choose_function", choose_function); } </pre> It can be used this way in Python: <pre> >>> from make_function_test import * >>> f = choose_function(1) >>> g = choose_function(0) >>> f() 'foo' >>> g() 'bar' </pre> <p>  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>