Draw-Movable-Rectangle.swift

let overlay = UIView()
var lastPoint = CGPoint.zero
    
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    clearOverlay()
    if let touch = touches.first {
        lastPoint = touch.location(in: self.view)
    }
}


override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        let currentPoint = touch.location(in: view)
        drawSelectionArea(fromPoint: lastPoint, toPoint: currentPoint)
    }
}

func drawSelectionArea(fromPoint: CGPoint, toPoint: CGPoint) {

        let rect = CGRect(x: min(fromPoint.x, toPoint.x), y: min(fromPoint.y, toPoint.y), width: abs(fromPoint.x - toPoint.x), height: abs(fromPoint.y - toPoint.y))
        overlay.frame = rect
}

func clearOverlay(){
      overlay.isHidden = false
      overlay.frame = CGRect.zero
}