SelectionMessage
BMessage* SelectionMessage() const;
BMessage* SelectionMessage();
BMessage* SelectionMessage() const;
BMessage* SelectionMessage() const
if (status == B_OK && SelectionMessage())
status = archive->AddMessage("_selectMsg", SelectionMessage());
if (SelectionMessage())
return SelectionMessage()->what;
InvokeNotify(SelectionMessage(), B_CONTROL_MODIFIED);