ceph/src/boost/libs/python/doc/reference/data_members.qbk

   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 ``
   7 template <class C, class D>
   8 object make_getter(D C::*pm);
   9
  10 template <class C, class D, class Policies>
  11 object 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<>
  16 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.]]
  17 [[Returns][An instance of object which holds the new Python callable object.]]
  18 ]
  19 ``
  20 template <class D>
  21 object make_getter(D const& d);
  22 template <class D, class Policies>
  23 object make_getter(D const& d, Policies const& policies);
  24
  25 template <class D>
  26 object make_getter(D const* p);
  27 template <class D, class Policies>
  28 object 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 ``
  36 template <class C, class D>
  37 object make_setter(D C::*pm);
  38
  39 template <class C, class D, class Policies>
  40 object 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 ``
  48 template <class D>
  49 object make_setter(D& d);
  50 template <class D, class Policies>
  51 object make_setter(D& d, Policies const& policies);
  52
  53 template <class D>
  54 object make_setter(D* p);
  55 template <class D, class Policies>
  56 object 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]
  65 The 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
  71 struct X
  72 {
  73     X(int x) : y(x) {}
  74     int y;
  75 };
  76
  77 using namespace boost::python;
  78
  79 BOOST_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 ``
  87 It can be used this way in Python:
  88 ``
  89 >>> from data_members_example import *
  90 >>> x = X(1)
  91 >>> x.get()
  92 1
  93 >>> x.set(2)
  94 >>> x.get()
  95 2
  96 ``
  97 [endsect]
  98 [endsect]