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

I have to create undo and redo performance utilizing swift UndoManager to my Paint app. I did it undo with eradicating final oject from array. However i need to use UndoManager. And if there’s some advices, possibly i’m doing one thing improper. If somebody may also help me, pls.

remaining class WACanvas: UIView {

    non-public var strains = [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 }
        
        strains.forEach { line in
            guard line.factors.rely > 1 else { return }
            print(line.factors)
            context.setStrokeColor(line.coloration.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?) {
        strains.append(WALine(coloration: 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 = strains.popLast() else { return }
        lastLine.factors.append(level)
        
        strains.append(lastLine)
        
        setNeedsDisplay()
    }
    
    // MARK: - Public strategies
    public func undo() {
        _ = strains.popLast()
        setNeedsDisplay()
    }
    
    public func clear() {
        strains.removeAll()
        setNeedsDisplay()
    }
    
    public func setSTrokeColor(coloration: UIColor) {
        self.strokeColor = coloration
    }
    
    public func setSTroke(width: Float) {
        self.strokeWidth = width
    }
}