1[section boost/python/data_members.hpp] 2[section Introduction] 3`make_getter()` and `make_setter()` are the functions used internally by [link high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel.class_template_class_modifier_fu `class_<>::def_readonly`] and [link high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel.class_template_class_modifier_fu `class_<>::def_readwrite`] to produce Python callable objects which wrap C++ data members. 4[endsect] 5[section Functions] 6`` 7template <class C, class D> 8object make_getter(D C::*pm); 9 10template <class C, class D, class Policies> 11object make_getter(D C::*pm, Policies const& policies); 12`` 13[variablelist 14[[Requires][Policies is a model of [link concepts.callpolicies `CallPolicies`].]] 15[[Effects][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<> 16for 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.]] 17[[Returns][An instance of object which holds the new Python callable object.]] 18] 19`` 20template <class D> 21object make_getter(D const& d); 22template <class D, class Policies> 23object make_getter(D const& d, Policies const& policies); 24 25template <class D> 26object make_getter(D const* p); 27template <class D, class Policies> 28object make_getter(D const* p, Policies const& policies); 29`` 30[variablelist 31[[Requires][Policies is a model of CallPolicies.]] 32[[Effects][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.]] 33[[Returns][An instance of object which holds the new Python callable object.]] 34] 35`` 36template <class C, class D> 37object make_setter(D C::*pm); 38 39template <class C, class D, class Policies> 40object make_setter(D C::*pm, Policies const& policies); 41`` 42[variablelist 43[[Requires][Policies is a model of CallPolicies.]] 44[[Effects][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.]] 45[[Returns][An instance of object which holds the new Python callable object.]] 46] 47`` 48template <class D> 49object make_setter(D& d); 50template <class D, class Policies> 51object make_setter(D& d, Policies const& policies); 52 53template <class D> 54object make_setter(D* p); 55template <class D, class Policies> 56object make_setter(D* p, Policies const& policies); 57`` 58[variablelist 59[[Requires][Policies is a model of CallPolicies.]] 60[[Effects][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.]] 61[[Returns][An instance of object which holds the new Python callable object.]] 62] 63[endsect] 64[section Example] 65The code below uses make_getter and make_setter to expose a data member as functions: 66`` 67#include <boost/python/data_members.hpp> 68#include <boost/python/module.hpp> 69#include <boost/python/class.hpp> 70 71struct X 72{ 73 X(int x) : y(x) {} 74 int y; 75}; 76 77using namespace boost::python; 78 79BOOST_PYTHON_MODULE_INIT(data_members_example) 80{ 81 class_<X>("X", init<int>()) 82 .def("get", make_getter(&X::y)) 83 .def("set", make_setter(&X::y)) 84 ; 85} 86`` 87It can be used this way in Python: 88`` 89>>> from data_members_example import * 90>>> x = X(1) 91>>> x.get() 921 93>>> x.set(2) 94>>> x.get() 952 96`` 97[endsect] 98[endsect] 99