SetMessage( message );
     SetWindowStyle(style);
     SetPath(defaultPath);
+    m_sheetDelegate = [[ModalDialogDelegate alloc] init];
+    [(ModalDialogDelegate*)m_sheetDelegate setImplementation: this];
+}
+
+wxDirDialog::~wxDirDialog()
+{
+    [m_sheetDelegate release];
 }
 
 void wxDirDialog::ShowWindowModal()
     if (parentWindow)
     {
         NSWindow* nativeParent = parentWindow->GetWXWindow();
-        ModalDialogDelegate* sheetDelegate = [[ModalDialogDelegate alloc] init];
-        [sheetDelegate setImplementation: this];
         [oPanel beginSheetForDirectory:dir.AsNSString() file:nil types: nil
-            modalForWindow: nativeParent modalDelegate: sheetDelegate
+            modalForWindow: nativeParent modalDelegate: m_sheetDelegate
             didEndSelector: @selector(sheetDidEnd:returnCode:contextInfo:)
             contextInfo: nil];
     }
 
 
 - (id) init
 {
-    [super init];
+    self = [super init];
     _dialog = NULL;
     return self;
 }
     : wxFileDialogBase(parent, message, defaultDir, defaultFileName, wildCard, style, pos, sz, name)
 {
     m_filterIndex = -1;
+    m_sheetDelegate = [[ModalDialogDelegate alloc] init];
+    [(ModalDialogDelegate*)m_sheetDelegate setImplementation: this];
+}
+
+wxFileDialog::~wxFileDialog()
+{
+    [m_sheetDelegate release];
 }
 
 bool wxFileDialog::SupportsExtraControl() const
         [sPanel setAllowsOtherFileTypes:NO];
         
         NSWindow* nativeParent = parentWindow->GetWXWindow();
-        ModalDialogDelegate* sheetDelegate = [[ModalDialogDelegate alloc] init];
-        [sheetDelegate setImplementation: this];
         [sPanel beginSheetForDirectory:dir.AsNSString() file:file.AsNSString()
-            modalForWindow: nativeParent modalDelegate: sheetDelegate
+            modalForWindow: nativeParent modalDelegate: m_sheetDelegate
             didEndSelector: @selector(sheetDidEnd:returnCode:contextInfo:)
             contextInfo: nil];
     }
         [oPanel setAllowsMultipleSelection: (HasFlag(wxFD_MULTIPLE) ? YES : NO )];
         
         NSWindow* nativeParent = parentWindow->GetWXWindow();
-        ModalDialogDelegate* sheetDelegate = [[ModalDialogDelegate alloc] init];
-        [sheetDelegate setImplementation: this];
         [oPanel beginSheetForDirectory:dir.AsNSString() file:file.AsNSString()
             types: types modalForWindow: nativeParent
-            modalDelegate: sheetDelegate
+            modalDelegate: m_sheetDelegate
             didEndSelector: @selector(sheetDidEnd:returnCode:contextInfo:)
             contextInfo: nil];
     }
 
                                  const wxPoint& WXUNUSED(pos))
                : wxMessageDialogBase(parent, message, caption, style)
 {
+    m_sheetDelegate = [[ModalDialogDelegate alloc] init];
+    [(ModalDialogDelegate*)m_sheetDelegate setImplementation: this];
+}
+
+wxMessageDialog::~wxMessageDialog()
+{
+    [m_sheetDelegate release];
 }
 
 int wxMessageDialog::ShowModal()
     if (parentWindow)
     {
         NSWindow* nativeParent = parentWindow->GetWXWindow();
-        ModalDialogDelegate* sheetDelegate = [[ModalDialogDelegate alloc] init];
-        [sheetDelegate setImplementation: this];
-        [alert beginSheetModalForWindow: nativeParent modalDelegate: sheetDelegate
+        [alert beginSheetModalForWindow: nativeParent modalDelegate: m_sheetDelegate
             didEndSelector: @selector(sheetDidEnd:returnCode:contextInfo:)
             contextInfo: nil];
     }