(thanks to Paintcode) Draw a hollow circle in swift, or just a piece of one... angle starts at bottom and rotates around clockwise.

Donut.swift

    class func drawHollowCircle(circleColor: UIColor, rect: CGRect, startAngle: CGFloat = 1, endAngle: CGFloat = 360, outerRingProportion: CGFloat = 1, innerRingProportion: CGFloat = 0.5, drawShadow : Bool) {
        
        //// Variable Declarations
        let startAngleCalced: CGFloat = -startAngle + 270
        let endAngleCalced: CGFloat = -endAngle + 270
        let innerRingDiameter: CGFloat = rect.size.width * innerRingProportion
        let innerRingOffset: CGFloat = 0.5 * (rect.size.width - innerRingDiameter)
        let innerRingRect = CGRectMake(innerRingOffset, innerRingOffset, innerRingDiameter, innerRingDiameter)
        let outerRingDiameter: CGFloat = rect.size.width * outerRingProportion
        let outerRingOffset: CGFloat = 0.5 * (rect.size.width - outerRingDiameter)
        let outerRingRect = CGRectMake(outerRingOffset, outerRingOffset, outerRingDiameter, outerRingDiameter)
        
        //// Outer Circle Drawing
        let outerCircleRect = outerRingRect
        let outerCirclePath = UIBezierPath()
        outerCirclePath.addArcWithCenter(CGPointMake(outerCircleRect.midX, outerCircleRect.midY), radius: outerCircleRect.width / 2, startAngle: -startAngleCalced * CGFloat(M_PI)/180, endAngle: -endAngleCalced * CGFloat(M_PI)/180, clockwise: true)
        outerCirclePath.addLineToPoint(CGPointMake(outerCircleRect.midX, outerCircleRect.midY))
        outerCirclePath.closePath()
        
        
        //// InnerCircle Drawing
        let innerCircleRect = innerRingRect
        let innerCirclePath = UIBezierPath()
        innerCirclePath.addArcWithCenter(CGPointMake(innerCircleRect.midX, innerCircleRect.midY), radius: innerCircleRect.width / 2, startAngle: -startAngleCalced * CGFloat(M_PI)/180, endAngle: -endAngleCalced * CGFloat(M_PI)/180, clockwise: true)
        innerCirclePath.addLineToPoint(CGPointMake(innerCircleRect.midX, innerCircleRect.midY))
        innerCirclePath.closePath()
        
        // Clip out the innerCirclePath
        outerCirclePath.appendPath(innerCirclePath)
        outerCirclePath.addClip()
        outerCirclePath.usesEvenOddFillRule = true;

        if (drawShadow) {
            CGContextSetShadowWithColor(UIGraphicsGetCurrentContext(), CGSizeZero, 0.25 * innerRingDiameter, circleColor.CGColor);
        }

        circleColor.setFill()
        outerCirclePath.fill()
    }