Swift 3视频;错误的指令错误

Question

我要做的就是拥有一个带按钮的视图控制器。按下它会播放视频。

我的代码有一个运行时错误指令错误。应用程序可以构建，但按下按钮时会出现错误消息。错误消息符合“let videoURL = NSURL（fileURLWithPath：filePath！）”。

import UIKit
import AVKit
import AVFoundation

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
@IBAction func playVideo(_ sender: UIButton) {

    playLocalVideo()

}
func playLocalVideo(){
    let filePath = Bundle.main.path(forResource: "t", ofType: "mp4")
    let videoURL = NSURL(fileURLWithPath: filePath!)
    let player = AVPlayer(url: videoURL as URL)
    let playViewController = AVPlayerViewController()

    playViewController.player = player
    self.present(playViewController, animated: true) {() -> Void in playViewController.player!.play()


} }  }