The update bar(slider) function

NSTimer

// in the mainView class we need to create an outlet for the slider, and the text label for the current time.
  @IBOutlet weak var audioPlayerBar: UISlider!
  @IBOutlet weak var timeViewer: UILabel!

// updating slider function 
func updateSlider(){
    let currentTime = Float(nsTimerToSeconds(audioPlayer.currentTime))
    audioPlayerBar.value = currentTime
    timeViewer.text = "\(currentTime) / \(audioLengthSeconds)"
}