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| <h1 align="center"><a href="../index.html">Boost.Python</a></h1> |
| |
| <h2 align="center">Header <call_method.hpp></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><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> |
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