class InterfaceController: WKInterfaceController {

    //... existing code...

    private var crownDelta = 0.0

    private var count: Int = 0 {
        didSet {
            setCount(count: String(count))
        }
    }

    override func awake(withContext context: Any?) {
        super.awake(withContext: context)

        // Configure interface objects here.

        crownSequencer.delegate = self
    }

    override func willActivate() {
        // This method is called when watch view controller is about to be visible to user
        super.willActivate()
        crownSequencer.focus()
    }
}

extension InterfaceController: WKCrownDelegate {

    func crownDidRotate(_ crownSequencer: WKCrownSequencer?, rotationalDelta: Double) {
        crownDelta += rotationalDelta
        if crownDelta > 0.1 {
            count += 1
            crownDelta = 0.0
        } else if crownDelta < -0.1 {
            count -= 1
            crownDelta = 0.0
        }
    }
}