NSUndoManager in CoreDataBooks example from Apple
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I'm writing an iPhone app using Apple's CoreDataBooks sample as a reference.

`NSUndoManager` is initialized but seems not to be used at all. When I shake the device while editing text in `UITextField` it shows me a popup with undo option but this appears to be standard `UITextField` behavior.

If I comment out `setUpUndoManager` function nothing changes.

So I have two questions:

1. Is `undoManager` useless in this sample or I just didn't manage to find how to use it's functionality from UI?

2. If former then I wonder what's the preferred way to support undo in applications like CoreDataBooks from user's perspective. Shall I add a toolbar with undo/redo buttons or something like that?

Thanks in advance.