UIView with a rounded progress border

ProgressBubble.swift

class ProgressBubble : UIView {
    var startAngle: Double = 90
    var lineWidth: CGFloat = 4
    var timer: Timer!
    var borderColor: UIColor = UIColor(colorLiteralRed: 248/255.0, green: 141/255.0, blue: 2/255.0, alpha: 1)
    
    override func draw(_ rect: CGRect) {
        self.drawBorder(rect, self.startAngle, self.borderColor)
    }
    
    fileprivate func drawBorder(_ frame: CGRect, _ startAngle: Double, _ borderColor: UIColor) {
        let ovalRect: CGRect = CGRect(x: frame.minX + self.lineWidth/2,
                                      y: frame.minY + self.lineWidth/2,
                                      width: frame.size.width - self.lineWidth,
                                      height: frame.size.height - self.lineWidth)
        
        let center = CGPoint(x: ovalRect.midX,
                             y: ovalRect.midY)
        
        let ovalPath = UIBezierPath()
        let start: CGFloat = CGFloat(Double(-90.0) * (M_PI / Double(180.0)))
        let end: CGFloat = CGFloat(Double(-startAngle) * (M_PI / Double(180.0)))

        ovalPath.addArc(withCenter: center, radius: ovalRect.width/2, startAngle: start, endAngle: end, clockwise: true)
        ovalPath.lineWidth = self.lineWidth
        
        borderColor.setStroke()
        ovalPath.stroke()
    }
    
    func startProgress() {
        let selector = #selector(self.fillBorder)
        self.timer = Timer.scheduledTimer(timeInterval: 0.05,
                                          target: self,
                                          selector: selector,
                                          userInfo: nil,
                                          repeats: true)
    }
    
    func stopProgress() {
        if self.timer.isValid {
            self.timer.invalidate()
        }
    }

    @objc fileprivate func fillBorder() {
        if self.startAngle <= -270 {
            self.timer.invalidate()
            self.startAngle = 90
            return
        }

        self.startAngle = self.startAngle - 10
        self.setNeedsDisplay()
    }
}