...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
make_getter()
and make_setter()
are the functions used internally by class_<>::def_readonly
and class_<>::def_readwrite
to produce Python
callable objects which wrap C++ data members.
template <class C, class D> object make_getter(D C::*pm); template <class C, class D, class Policies> object make_getter(D C::*pm, Policies const& policies);
Policies is a model of CallPolicies
.
Creates a Python callable object which accepts a single argument that can be converted from_python to C*, and returns the corresponding member D member of the C object, converted to_python. If policies is supplied, it will be applied to the function as described here. Otherwise, the library attempts to determine whether D is a user-defined class type, and if so uses return_internal_reference<> for Policies. Note that this test may inappropriately choose return_internal_reference<> in some cases when D is a smart pointer type. This is a known defect.
An instance of object which holds the new Python callable object.
template <class D> object make_getter(D const& d); template <class D, class Policies> object make_getter(D const& d, Policies const& policies); template <class D> object make_getter(D const* p); template <class D, class Policies> object make_getter(D const* p, Policies const& policies);
Policies is a model of CallPolicies.
Creates a Python callable object which accepts no arguments and returns d or *p, converted to_python on demand. If policies is supplied, it will be applied to the function as described here. Otherwise, the library attempts to determine whether D is a user-defined class type, and if so uses reference_existing_object for Policies.
An instance of object which holds the new Python callable object.
template <class C, class D> object make_setter(D C::*pm); template <class C, class D, class Policies> object make_setter(D C::*pm, Policies const& policies);
Policies is a model of CallPolicies.
Creates a Python callable object which, when called from Python, expects two arguments which can be converted from_python to C* and D const&, respectively, and sets the corresponding D member of the C object. If policies is supplied, it will be applied to the function as described here.
An instance of object which holds the new Python callable object.
template <class D> object make_setter(D& d); template <class D, class Policies> object make_setter(D& d, Policies const& policies); template <class D> object make_setter(D* p); template <class D, class Policies> object make_setter(D* p, Policies const& policies);
Policies is a model of CallPolicies.
Creates a Python callable object which accepts one argument, which is converted from Python to D const& and written into d or *p, respectively. If policies is supplied, it will be applied to the function as described here.
An instance of object which holds the new Python callable object.
The code below uses make_getter and make_setter to expose a data member as functions:
#include <boost/python/data_members.hpp> #include <boost/python/module.hpp> #include <boost/python/class.hpp> struct X { X(int x) : y(x) {} int y; }; using namespace boost::python; BOOST_PYTHON_MODULE_INIT(data_members_example) { class_<X>("X", init<int>()) .def("get", make_getter(&X::y)) .def("set", make_setter(&X::y)) ; }
It can be used this way in Python:
>>> from data_members_example import * >>> x = X(1) >>> x.get() 1 >>> x.set(2) >>> x.get() 2