private func drawDashedLine() {
  let shapeLayer = CAShapeLayer()
  let bezierPath = UIBezierPath()

  let pointA = CGPoint(x: self.bounds.minX, y: self.bounds.midY)
  let pointB = CGPoint(x: self.bounds.maxX, y: self.bounds.midY)

  bezierPath.move(to: pointA)
  bezierPath.addLine(to: pointB)

  shapeLayer.fillColor = UIColor.white.cgColor
  shapeLayer.strokeColor = UIColor.white.cgColor
  shapeLayer.lineWidth = 2.0 / UIScreen.main.scale
  shapeLayer.lineJoin = kCALineJoinMiter
  shapeLayer.lineDashPattern = [ 6, 3 ]
  shapeLayer.path = bezierPath.cgPath
  backgroundColor = dashColor
  layer.mask = shapeLayer
}