Creating a simple timer in WatchOS with Swift 4

Question

Seemingly simple but I'm struggling...the code below crashes on the line setting the date of the workoutTimer. Also my WKInterfaceTimer isn't hooked up to an IBOutlet, does it need to be? I wanted to use it just for purposes of the time.

class InterfaceController { 
            var workoutTimer: WKInterfaceTimer!
            var workoutStartTime: NSDate? = nil

    func startWorkOutTimer() {
   self.startWorkout()
            if let test = self.workoutSecondsElapsed() {
            print("timer seconds = \(test)")
            }
}


    func startWorkout() {
        // To count up use 0.0 or less, otherwise the timer counts down.
        workoutTimer.setDate(NSDate(timeIntervalSinceNow: 0.0) as Date)
        workoutTimer.start()
        self.workoutStartTime = NSDate()
    }

    func stopWorkout() {
        workoutTimer.stop()
    }

    func workoutSecondsElapsed() -> TimeInterval? {
        // If the timer hasn't been started then return nil
        guard let startTime = self.workoutStartTime else {
            return nil
        }
        // Time intervals from past dates are negative, so
        // multiply by -1 to get the elapsed time.
        return -1.0 * (self.workoutStartTime?.timeIntervalSinceNow)!
    }

}

Answer 1

From Apple doc:

Do not subclass or create instances of this class yourself. Instead, define outlets in your interface controller class and connect them to the corresponding objects in your storyboard file.

Your app probably is crashing because your timer is nil, but for what you need you can use Timer class instead of WKInterfaceTimer.