I can't get an arc to fill in Swift 4

Question

I have a class that makes a UIView of a circle. I when I add the circle to my view, it shows the red outline, but the interior is clear instead of black. I want it to have a black fill.

class CircleView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
        self.backgroundColor = UIColor.clear
    }

    required init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }


    override func draw(_ rect: CGRect) {
        if let context = UIGraphicsGetCurrentContext() {

            context.setLineWidth(1.0);

            UIColor.red.set()

            let center = CGPoint(x: frame.size.width/2, y: frame.size.height/2)
            let radius = (frame.size.width - 10)/2
            context.addArc(center: center, radius: radius, startAngle: 0.0, endAngle: .pi * 2.0, clockwise: true)

            context.strokePath()
            context.closePath()
            context.setFillColor(UIColor.black.cgColor)
            context.fillPath()
        }
    }


}

Answer 1

If you look to the documentation of strokePath():

The current path is cleared as a side effect of calling this function.

Basically, after stroking your path, your paths is reset and there is nothing to fill.

A workaround could be to save context.path first and then use context.addPath(path). However, I usually prefer to build a separate CGMutablePath first and then add it to the context.