interface/weakref.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        weakref.h
   3 // Purpose:     interface of wxWeakRefDynamic<T>
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10     @wxheader{weakref.h}
  11
  12     wxWeakRefDynamicT is a template class for weak references that is used in
  13     the same way as wxWeakRefT. The only difference is that wxWeakRefDynamic
  14     defaults to using @c dynamic_cast for establishing the object
  15     reference (while wxWeakRef defaults to @c static_cast).
  16
  17     So, wxWeakRef will detect a type mismatch during compile time and will
  18     have a little better run-time performance. The role of wxWeakRefDynamic
  19     is to handle objects which derived type one does not know.
  20
  21     @b Note: wxWeakRefT selects an implementation based on the static type
  22     of T. If T does not have wxTrackable statically, it defaults to to a mixed-
  23     mode operation, where it uses @c dynamic_cast as the last measure (if
  24     available from the compiler and enabled when building wxWidgets).
  25
  26     For general cases, wxWeakRefT is the better choice.
  27
  28     For API documentation, see: wxWeakRef
  29
  30     @library{wxcore}
  31     @category{FIXME}
  32 */
  33 class wxWeakRefDynamic<T>
  34 {
  35 public:
  36
  37 };
  38
  39
  40
  41 /**
  42     @wxheader{weakref.h}
  43
  44     wxWeakRef is a template class for weak references to wxWidgets objects,
  45     such as wxEvtHandler, wxWindow and
  46     wxObject. A weak reference behaves much like an ordinary
  47     pointer, but when the object pointed is destroyed, the weak reference is
  48     automatically reset to a @NULL pointer.
  49
  50     wxWeakRefT can be used whenever one must keep a pointer to an object
  51     that one does not directly own, and that may be destroyed before the object
  52     holding the reference.
  53
  54     wxWeakRefT is a small object and the mechanism behind it is fast
  55     (@b O(1)). So the overall cost of using it is small.
  56
  57     @library{wxbase}
  58     @category{FIXME}
  59
  60     @see wxSharedPtr, wxScopedPtr
  61 */
  62 class wxWeakRef<T>
  63 {
  64 public:
  65     /**
  66         Constructor. The weak reference is initialized to @e pobj.
  67     */
  68     wxWeakRefT(T* pobj = NULL);
  69
  70     /**
  71         Destructor.
  72     */
  73     ~wxWeakRefT();
  74
  75     /**
  76         Called when the tracked object is destroyed. Be default sets
  77         internal pointer to @NULL.
  78     */
  79     virtual void OnObjectDestroy();
  80
  81     /**
  82         Release currently tracked object and rests object reference.
  83     */
  84     void Release();
  85
  86     /**
  87         Returns pointer to the tracked object or @NULL.
  88     */
  89     T* get() const;
  90
  91     /**
  92         Release currently tracked object and start tracking the same object as
  93         the wxWeakRef @e wr.
  94     */
  95     T* operator =(wxWeakRef<T>& wr);
  96
  97     /**
  98         Implicit conversion to T*. Returns pointer to the tracked
  99         object or @NULL.
 100     */
 101     T* operator*() const;
 102
 103     /**
 104         Returns a reference to the tracked object. If the internal pointer is @NULL
 105         this method will cause an assert in debug mode.
 106     */
 107     T operator*() const;
 108
 109     /**
 110         Smart pointer member access. Returns a pointer to the
 111         tracked object. If the internal pointer is @NULL this
 112         method will cause an assert in debug mode.
 113     */
 114     T* operator-();
 115
 116     /**
 117         Releases the currently tracked object and starts tracking @e pobj.
 118         A weak reference may be reset by passing @e @NULL as @e pobj.
 119     */
 120     T* operator=(T* pobj);
 121 };
 122