UndoManager.WillRedoChangeMessage
A message that an undo manager sends before redoing a change.
Declaration
struct WillRedoChangeMessageOverview
The undo manager posts this message after you call redo(). Because this is a “will”-style message, the undo manager sends the message before it performs the redo.
Observe this message with the identifier willRedoChange, or specify its type directly to the addObserver(of:for:using:) method. The Subject of this message type is UndoManager.
This message interoperates with the notification NSUndoManagerWillRedoChange. The system notifies observers of the message when the NotificationCenter posts the notification. Similarly, the system notifies observers of the notification when it posts the message.