swift add horizontal line uiview programmatically

// create path

let path = UIBezierPath()
path.move(to: CGPoint(x: 10, y: 10))
path.addLine(to: CGPoint(x: 100, y: 100))

// Create a `CAShapeLayer` that uses that `UIBezierPath`:

let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.strokeColor = UIColor.blue.cgColor
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.lineWidth = 3

// Add that `CAShapeLayer` to your view's layer:

view.layer.addSublayer(shapeLayer)