AudioPlayer.swift

var curNode = AVAudioPlayerNode()

func play() {
  curNode.play();
  NotificationCenter.default.post(name: Notification.Name(rawValue: audioPlayerDidStartPlaying), object: self)
}

func pause() {
  curNode.pause();
  NotificationCenter.default.post(name: Notification.Name(rawValue: audioPlayerDidPause), object: self)
}

MainController.swift

let audioPlayerDidPause = "com.jcmoods.audioPlayerDidPauseNotificationKey";
let audioPlayerDidStartPlaying = "com.jcmoods.audioPlayerDidStartPlayingNotificationKey";

var paused: Bool? = true
var player: AudioPlayer;

func play() {
  player.play();
}

func pause() {
  player.pause();
}

func playerDidStartPlaying() {
  paused = false;
  print("playing");
}

func playerDidPause() {
    paused = true
    print("pause called")
}

override func viewDidLoad() {
  player = new AudioPlayer();
  NotificationCenter.default.addObserver(self, selector: "playerDidStartPlaying", name: NSNotification.Name(rawValue: audioPlayerDidStartPlaying), object: nil)
  NotificationCenter.default.addObserver(self, selector: "playerDidPause", name: NSNotification.Name(rawValue: audioPlayerDidPause), object: nil) 
}