How do I register UndoManager in Swift?

Question

How do I use UndoManager (previously NSUndoManager) in Swift?

Here\'s an Objective-C example I\'ve tried to replicate:

[[un         


        

Answer 1

I tried for 2 days to get Joshua Nozzi's answer to work in Swift 3, but no matter what I did the values were not captured. See: NSUndoManager: capturing reference types possible?

I gave up and just managed it myself by keeping track of changes in undo and redo stacks. So, given a person object I would do something like

protocol Undoable {
     func undo()
     func redo()
}

class Person: Undoable {

    var name: String {
        willSet {
             self.undoStack.append(self.name)
        }
    }
    var undoStack: [String] = []
    var redoStack: [String] = []

    init(name: String) {
        self.name = name
    }

    func undo() {
        if self.undoStack.isEmpty { return }
        self.redoStack.append(self.name)
        self.name = self.undoStack.removeLast()
    }

    func redo() {
        if self.redoStack.isEmpty { return }
        self.undoStack.append(self.name)
        self.name = self.redoStack.removeLast()
    }
}

Then to call it, I don't worry about passing arguments or capturing values since the undo/redo state is managed by the object itself. So say you have a ViewController that is managing your Person objects, you just call registerUndo and pass nil

undoManager?.registerUndo(withTarget: self, selector:#selector(undo), object: nil)