ios – How am i able to implement undoManager and make undo(), redo() capabilities?

I must create undo and redo performance utilizing swift UndoManager to my Paint app. I did it undo with eradicating final oject from array. However i wish to use UndoManager. And if there may be some advices, perhaps i’m doing one thing fallacious. If somebody may help me, pls.

remaining class WACanvas: UIView {

non-public var traces = [WALine]()
non-public var strokeColor = UIColor.black
non-public var strokeWidth: Float = 1

override func draw(_ rect: CGRect) {
    tremendous.draw(rect)
    
    guard let context = UIGraphicsGetCurrentContext() else { return }
    
    traces.forEach { line in
        guard line.factors.depend > 1 else { return }
        print(line.factors)
        context.setStrokeColor(line.colour.cgColor)
        context.setLineWidth(CGFloat(line.width))
        context.setLineCap(.spherical)
        
        context.transfer(to: line.factors.first!)
        context.addLines(between: line.factors)
        context.strokePath()
    }
}

override func touchesBegan(_ touches: Set, with occasion: UIEvent?) {
    traces.append(WALine(colour: strokeColor, width: strokeWidth, factors: []))
}

override func touchesMoved(_ touches: Set, with occasion: UIEvent?) {
    guard let level = touches.first?.location(in: self) else { return }
    
    guard var lastLine = traces.popLast() else { return }
    lastLine.factors.append(level)
    
    traces.append(lastLine)
    
    setNeedsDisplay()
}

// MARK: - Public strategies
public func undo() {
    _ = traces.popLast()
    setNeedsDisplay()
}

public func clear() {
    traces.removeAll()
    setNeedsDisplay()
}

public func setSTrokeColor(colour: UIColor) {
    self.strokeColor = colour
}

public func setSTroke(width: Float) {
    self.strokeWidth = width
}

}