iOS addLayer: how to layout right? - ios

Question

When adding some dash line to the view of a viewController, by add sublayer.
Here is the code:
class ViewController: UIViewController {
#IBOutlet weak var tmpLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
tmpLabel.layer.borderColor = UIColor.red.cgColor;
tmpLabel.layer.borderWidth = 2
tmpLabel.addDashedBorders(padding: 50, y: tmpLabel.bounds.size.height * 0.5)
// ......
}}
extension UIView {
func addDashedBorders( padding x: CGFloat, y : CGFloat) {
//Create a CAShapeLayer
let shapeLayer = CAShapeLayer()
shapeLayer.strokeColor = UIColor.red.cgColor
shapeLayer.lineWidth = 2
shapeLayer.lineDashPattern = [2,3]
let path = CGMutablePath()
path.addLines(between: [CGPoint(x: x, y: y),
CGPoint(x: bounds.size.width * 0.5 - 50, y: y)])
path.addLines(between: [CGPoint(x: bounds.size.width * 0.5 + 50, y: y),
CGPoint(x: bounds.size.width - x, y: y)])
shapeLayer.path = path
layer.addSublayer(shapeLayer)
}
}
The following image is in iPhoneX
The code is hard-coded, and not good.
I want to add the sub shape layer to the view , right beneath the label.
there is the code
class ViewController: UIViewController {
#IBOutlet weak var tmpLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
tmpLabel.layer.borderColor = UIColor.red.cgColor;
tmpLabel.layer.borderWidth = 2
view.addDashedBorder(padding: 50, y: tmpLabel.frame.origin.y)
//...
}}
extension UIView {
func addDashedBorder( padding x: CGFloat, y : CGFloat) {
let shapeLayer = CAShapeLayer()
shapeLayer.strokeColor = UIColor.red.cgColor
shapeLayer.lineWidth = 2
shapeLayer.lineDashPattern = [2,3]
let path = CGMutablePath()
path.addLines(between: [CGPoint(x: x, y: y),
CGPoint(x: bounds.size.width - x, y: y)])
shapeLayer.path = path
layer.addSublayer(shapeLayer)
}
}
I tested in iPhoneX, there is a distance.
I tried view.safeAreaInsets, it is all zero.
What do I miss?