1. 实现

//MARK:- 绘制虚线
func drawDashLine(strokeColor: UIColor, lineWidth: CGFloat = 1, lineLength: Int = 10, lineSpacing: Int = 5, isBottom: Bool = true) {
    let shapeLayer = CAShapeLayer()
    shapeLayer.bounds = self.bounds
    shapeLayer.anchorPoint = CGPoint(x: 0, y: 0)
    shapeLayer.fillColor = UIColor.blue.cgColor
    shapeLayer.strokeColor = strokeColor.cgColor
    
    shapeLayer.lineWidth = lineWidth
    shapeLayer.lineJoin = kCALineJoinRound
    
    //每一段虚线长度 和 每两段虚线之间的间隔
    shapeLayer.lineDashPattern = [NSNumber(value: lineLength), NSNumber(value: lineSpacing)]
    
    let path = CGMutablePath()
    let y = isBottom == true ? self.layer.bounds.height - lineWidth : 0
    path.move(to: CGPoint(x: 0, y: y))
    path.addLine(to: CGPoint(x: self.layer.bounds.width, y: y))
    shapeLayer.path = path
    self.layer.addSublayer(shapeLayer)
}

2. 使用方法

let view1 = UIView(frame: CGRect(x: 50, y: 100, width: 300, height: 30))
view1.backgroundColor = UIColor.red
view1.drawDashLine(strokeColor: UIColor.black)
view.addSubview(view1)