NSUndoManager in a storyboard-based macOS app

The MacOS application template in a newer version of Xcode defaults to using storyboards. To implement custom Undo and Redo operations it is necessary to implement to have your NSView implement NSWindowDelegate.

Create an NSUndoManager for the view:

NSUndoManager* undoManager;

Assign the delegate programmatically within initWithFrame and set your view as the first responder:

NSWindow* mainWindow = [[[NSApplication sharedApplication] windows] objectAtIndex:0];
mainWindow.delegate = self;
undoManager = [[NSUndoManager alloc] init];
    [self becomeFirstResponder];

Then in the method where the undoable action takes place

[[undoManager prepareWithInvocationTarget:self] undoAction];

if(![undoManager isUndoing]) {
    [undoManager setActionName:@"Select"];
} 

Where undoAction is the method on your view.

For a working example see this LifeView.m in my Game of Life cocoa app.