制御文が呼ばれない

MainStoryBoard上にタップするとオーディオを再生し、再生中のbackground colorが変更されるUIButtonを2つ設置しています。yourButton、yourButton2になります。

MainStoryBoard上に新たにyourButton、yourButton2のオーディオを順番に再生するyourButton3を設置したのですが、以下のコードで試してみると
else if文の三番目のaudioPlayerdidFinishPlayingが呼ばれません。

   let url1 = Bundle.main.bundleURL.appendingPathComponent("music1.mp3")
   let url2 = Bundle.main.bundleURL.appendingPathComponent("music2.mp3")

   @IBOutlet weak var yourButton: customButton!
   @IBOutlet weak var yourButton2: customButton!
   @IBOutlet weak var yourButton3: customButton!


   fileprivate var player1:AVAudioPlayer?
   fileprivate var player2:AVAudioPlayer?
   fileprivate var player3:AVAudioPlayer?


  @IBAction func pushButton1(sender: UIButton) {
       Player(url: url1)
   }

  @IBAction func pushButton2(sender: UIButton) {
    Player1(url: url2)
   }

  @IBAction func pushButton3(_ sender: UIButton) {
    Player(url: url2)
    player1!.play()

   }


  func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool) {
    if (player === player1) {
        yourButton.isSelected = false
    } else if (player === player2) {
        yourButton2.isSelected = false
    } else if (player === player3) {
        yourButton.isSelected = false
        player2!.play()
        yourButton2.isSelected = false
    }
}



  func Player(url: URL) {
    do {
        try player1 = AVAudioPlayer(contentsOf:url)
        player1!.play()
        yourButton.isSelected = true
        player1!.delegate = self
    } catch {
        print(error)
    }
}

  func Player1(url: URL) {
    do {
        try player2 = AVAudioPlayer(contentsOf:url)
        player2!.play()
        yourButton2.isSelected = true
        player2!.delegate = self

    } catch {
        print(error)
    }
}

  func Player3(url: URL, url2: URL) {
    do {
        try player1 = AVAudioPlayer(contentsOf:url)
        try player2 = AVAudioPlayer(contentsOf: url2)
        player1!.play()
        yourButton.isSelected = true
        player1!.delegate = self
    } catch {
        print(error)
    }
}

以下の文で解決しました！

func
1    if (player === player1) {
2        yourButton.isSelected = false
3    } else if (player === player2) {
4        yourButton2.isSelected = false
5    }
6}
7コード