Add computed properties to NSTimeInterval to return component parts of a time interval

MyFirstExtension.swift

extension NSTimeInterval {
    
    var inHours: Double { return self.inMinutes/60 } // express the time interval in hours
    var inMinutes: Double { return self/60 } // express the time interval in minutes
    var inSeconds: Double { return self } // express the time interval in seconds
    
    // express the time interval in hours, minutes and seconds
    var inHoursMinutesSeconds: (hours: Double, minutes: Double, seconds: Double) {
        let hours: Double = floor(round(self) / 60 / 60)
        let minutes: Double = trunc((round(self) - (hours * 60 * 60)) / 60)
        let seconds: Double = trunc(round(self) - minutes * 60)
        return (hours: hours, minutes: minutes, seconds: seconds)
    }
    
    // express the time interval in minutes and seconds
    var inMinutesSeconds: (minutes: Double, seconds: Double) {
        let minutes: Double = floor(round(self) / 60)
        let seconds: Double = trunc(round(self) - minutes * 60)
        return (minutes: minutes, seconds: seconds)
    }
}

func setTimerLabel {
    timerLabel.text = String(format: "%02.0f:%02.0f", remainingIntervalDuration.inMinutesSeconds.minutes, remainingIntervalDuration.inMinutesSeconds.seconds)
}