ios - xcode9 swift4 fatal error : Unexpectedly found nil while unwrapping an Optional value

Question

我尝试在应用程序启动时播放 mp3 文件(5 秒)，但不断收到错误消息:

Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

import UIKit
import AudioToolbox

class ViewController: UIViewController {

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

    //create SystemSoundID
    var soundID:SystemSoundID = 0
    let path = Bundle.main.path(forResource: "iPhone100Voice", ofType: "mp3")
    let baseURL = NSURL(fileURLWithPath: path!)
    AudioServicesCreateSystemSoundID(baseURL, &soundID)
    //play
    AudioServicesPlaySystemSound(soundID)

    }

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
    }

}

谁能解释一下为什么以及如何解决这个问题？

Answer 1

检查以下几点，所有条件都必须为真:

• 该文件是否在项目导航器中？
• 是否在文件检查器中选中了目标成员资格复选框(要使其选中文件并按⌥⌘1)
• 文件名拼写是否正确(iPhone100Voice.mp3)？