The Core iOS Developer’s Cookbook, Fifth Edition

Adding Undo/Redo Support

Core Data simplifies table undo/redo support to an astonishing degree. It provides automatic support for these operations and requires little programming effort. Add this support by assigning an undo manager when you create a Core Data context:

Click here to view code image

_context = [[NSManagedObjectContext alloc] init]; _context.persistentStoreCoordinator = persistentStoreCoordinator; _context.undoManager = [[NSUndoManager alloc] init]; _context.undoManager.levelsOfUndo = 999;

As with all other undo/redo support, your primary controller must become the first responder while it is onscreen. The standard suite of first responder methods includes canBecomeFirstResponder (respond YES), viewDidAppear: (the controller view ...