include/wx/weakref.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/weakref.h
   3 // Purpose:     wxWeakRef - Generic weak references for wxWidgets
   4 // Author:      Arne Steinarson
   5 // Created:     2007-12-27
   6 // RCS-ID:      $Id:$
   7 // Copyright:   (c) 2007 Arne Steinarson
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 #ifndef _WX_WEAKREF_H_
  12 #define _WX_WEAKREF_H_
  13
  14 #include <wx/tracker.h>
  15
  16 // A weak reference to an object of type T, where T has type wxTrackable
  17 // as one of its base classes (in a static or dynamic sense).
  18 template<class T>
  19 class wxWeakRef : public wxTrackerNode
  20 {
  21 public:
  22     wxWeakRef(T *pobj = NULL) : m_pobj(NULL) { Assign(pobj); }
  23
  24     virtual ~wxWeakRef() { Assign(NULL); }
  25
  26     // Smart pointer functions
  27     operator T*(){ return m_pobj; }
  28     T* operator->(){ return m_pobj; }
  29     T* operator=(T *pobj)
  30     {
  31         Assign(pobj);
  32         return m_pobj;
  33     }
  34
  35     virtual void OnObjectDestroy()
  36     {
  37         // Tracked object itself removes us from list of trackers
  38         wxASSERT( m_pobj );
  39         m_pobj = NULL;
  40     }
  41
  42     virtual wxTrackerNodeType GetType() { return WeakRef; }
  43
  44 protected:
  45     wxTrackableBase *GetTrackable(T *pobj)
  46     {
  47         // this uses static_cast if possible or dynamic_cast otherwise
  48         return wxTrackableCaster<T, wxHasBase<T, wxTrackableBase>::value>
  49                 ::Cast(pobj);
  50     }
  51
  52     void Assign(T* pobj)
  53     {
  54         if ( m_pobj == pobj )
  55             return;
  56
  57         // First release old object if any
  58         if ( m_pobj )
  59         {
  60             // Remove ourselves from object tracker list
  61             GetTrackable(m_pobj)->RemoveNode(this);
  62             m_pobj = NULL;
  63         }
  64
  65         // Now set new trackable object
  66         if ( pobj )
  67         {
  68             wxTrackableBase * const pt = GetTrackable(pobj);
  69             wxCHECK_RET( pt, "type must derive from wxTrackableBase" );
  70
  71             pt->AddNode(this);
  72             m_pobj = pobj;
  73         }
  74     }
  75
  76     T *m_pobj;
  77 };
  78
  79 // Provide some basic types of weak references
  80 class WXDLLIMPEXP_FWD_BASE wxObject;
  81 class WXDLLIMPEXP_FWD_BASE wxEvtHandler;
  82 class WXDLLIMPEXP_FWD_CORE wxWindow;
  83
  84 typedef wxWeakRef<wxObject>      wxObjectRef;
  85 typedef wxWeakRef<wxEvtHandler>  wxEvtHandlerRef;
  86 typedef wxWeakRef<wxWindow>      wxWindowRef;
  87
  88 #endif // _WX_WEAKREF_H_
  89