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

   1 [section boost/python/pointee.hpp]
   2 [section Introduction]
   3 <boost/python/pointee.hpp> introduces a traits metafunction `template pointee<T>` that can be used to extract the "pointed-to" type from the type of a pointer or smart pointer.
   4 [endsect]
   5 [section Class template `pointee`]
   6 `pointee<T>` is used by the [link high_level_components.boost_python_class_hpp.class_template_class_t_bases_hel `class_<...>`] template to deduce the type being held when a pointer or smart pointer type is used as its HeldType argument.
   7 ``
   8 namespace boost { namespace python
   9 {
  10    template <class T> struct pointee
  11    {
  12       typedef T::element_type type;
  13    };
  14
  15    // specialization for pointers
  16    template <T> struct pointee<T*>
  17    {
  18       typedef T type;
  19    };
  20 }
  21 ``
  22 [endsect]
  23 [section Examples]
  24 Given a 3rd-party smart pointer type `smart_pointer<T>`, one might partially specialize `pointee<smart_pointer<T> >` so that it can be used as the HeldType for a class wrapper:
  25 ``
  26 #include <boost/python/pointee.hpp>
  27 #include <boost/python/class.hpp>
  28 #include <third_party_lib.hpp>
  29
  30 namespace boost { namespace python
  31 {
  32   template <class T> struct pointee<smart_pointer<T> >
  33   {
  34      typedef T type;
  35   };
  36 }}
  37
  38 BOOST_PYTHON_MODULE(pointee_demo)
  39 {
  40    class_<third_party_class, smart_pointer<third_party_class> >("third_party_class")
  41       .def(...)
  42       ...
  43       ;
  44 }
  45 ``
  46 [endsect]
  47 [endsect]