81 lines
2.3 KiB
Plaintext
81 lines
2.3 KiB
Plaintext
[section boost/python/call_method.hpp]
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[section Introduction]
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<boost/python/call_method.hpp> defines the call_method family of overloaded function templates, used to invoke callable attributes of Python objects from C++.
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[endsect]
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[section Function `call_method`]
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``
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template <class R, class A1, class A2, ... class An>
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R call_method(PyObject* self, char const* method, A1 const&, A2 const&, ... An const&)
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``
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[variablelist
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[[Requires][`R` is a pointer type, reference type, or a complete type with an accessible copy constructor]]
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[[Effects][Invokes `self.method(a1, a2, ...an)` in Python, where `a1...an` are the arguments to `call_method()`, converted to Python objects. For a complete semantic description, see this page.]]
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[[Returns][The result of the Python call, converted to the C++ type `R`.]]
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[[Rationale][`call_method` is critical to implementing C++ virtual functions which are overridable in Python, as shown by the example below.]]
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]
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[endsect]
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[section Example]
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The following C++ illustrates the use of `call_method` in wrapping a class with a virtual function that can be overridden in Python:
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C++ Module Definition
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``
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#include <boost/python/module.hpp>
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#include <boost/python/class.hpp>
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#include <boost/utility.hpp>
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#include <cstring>
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// class to be wrapped
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class Base
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{
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public:
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virtual char const* class_name() const { return "Base"; }
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virtual ~Base();
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};
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bool is_base(Base* b)
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{
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return !std::strcmp(b->class_name(), "Base");
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}
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// Wrapper code begins here
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using namespace boost::python;
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// Callback class
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class Base_callback : public Base
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{
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public:
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Base_callback(PyObject* self) : m_self(self) {}
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char const* class_name() const { return call_method<char const*>(m_self, "class_name"); }
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char const* Base_name() const { return Base::class_name(); }
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private:
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PyObject* const m_self;
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};
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using namespace boost::python;
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BOOST_PYTHON_MODULE(my_module)
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{
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def("is_base", is_base);
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class_<Base,Base_callback, noncopyable>("Base")
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.def("class_name", &Base_callback::Base_name)
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;
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}
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``
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Python code:
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``
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>>> from my_module import *
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>>> class Derived(Base):
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... def __init__(self):
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... Base.__init__(self)
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... def class_name(self):
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... return self.__class__.__name__
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...
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>>> is_base(Base()) # calls the class_name() method from C++
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1
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>>> is_base(Derived())
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0
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``
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[endsect]
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[endsect]
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