如何处理AVAudioPlayer在Swift中是可选的？

Question

I have a controller that may or may not play audio on viewdidload and therefore need to stop the audio from playing on viewwilldisappear.

It seems this sample code doesn't work if no audio is playing (crashes on .playing) because the audioPlayer isn't nil, but also hasn't been properly init'd (and doesn't need to be because there will be no audio)

var audioPlayer = AVAudioPlayer()

override func viewDidLoad() {
    if let uwStoryAudio = story.audioFile {
        var error:NSError?
        audioPlayer = AVAudioPlayer(contentsOfURL: uwStoryAudio, error: &error)
        audioPlayer.prepareToPlay()
        audioPlayer.play()
    }
}

override func viewWillDisappear(animated: Bool) {
    if audioPlayer.playing //CRASH
    {
        audioPlayer.stop()
    }
}

This is what I've currently got, using an Optional but I don't think it's "correct" / best practice...

var audioPlayer: AVAudioPlayer?

override func viewDidLoad() {
    if let uwStoryAudio = uwStory.audioFile {
        var error:NSError?
        audioPlayer = AVAudioPlayer(contentsOfURL: uwStoryAudio, error: &error)
        audioPlayer!.prepareToPlay()
        audioPlayer!.play()
    }
}

override func viewWillDisappear(animated: Bool) {
    if let uwAudioPlayer = audioPlayer
    {
        uwAudioPlayer.stop()
    }
}

Is there a better way of doing this?

Answer 1

No, that's it. Why do you think it's wrong? The optional says it may be nil, so you need to check for nil - which you are doing correctly.

Also, add in the playing check like this:

if let uwAudioPlayer = self.audioPlayer {
    if uwAudioPlayer.playing { etc