斯威夫特：所需条件为假：文件！= nil答案

【问题标题】：Swift: required condition is false: file != nil斯威夫特：所需条件为假：文件！= nil
【发布时间】：2015-05-10 22:33:29
【问题描述】：

该应用程序运行良好，但只要我点击 ChimunkButton，应用程序就会崩溃并提供以下错误：

错误：AVAudioPlayerNode.mm:678：-[AVAudioPlayerNode scheduleFile:atTime:completionHandler:]：所需条件为假：文件！= nil 2015-05-10 17:24:25.269 Pitch Perfect[50278:1897012] *** 由于未捕获的异常而终止应用程序 'com.apple.coreaudio.avfaudio'，原因：'所需条件为假：文件！= nil'

import UIKit
import AVFoundation

class PlaySoundsViewController: UIViewController {

    var audioRecording = AVAudioPlayer()
    var receivedAudio:RecordedAudio!
    var audioEngine:AVAudioEngine!
    var audioFile:AVAudioFile!



    func setupAudioPlayerWithFile(file:NSString, type:NSString) -> AVAudioPlayer  {


        //1
        var path = NSBundle.mainBundle().pathForResource(file as String, ofType: type as String)
        var url = NSURL.fileURLWithPath(path!)

        //2
        var error: NSError?

        //3
        var audioPlayer:AVAudioPlayer?
        audioPlayer = AVAudioPlayer(contentsOfURL: url, error: &error)

        //4
        return audioPlayer!
    }


    override func viewDidLoad() {
        super.viewDidLoad()


        audioRecording = AVAudioPlayer(contentsOfURL: receivedAudio.filePathUrl, error: nil)
        audioRecording.enableRate = true

        audioEngine = AVAudioEngine()

            }

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

    @IBAction func slowButton(sender: UIButton) {

        playButtons()
        audioRecording.rate = 0.5

    }


    @IBAction func fastSound(sender: UIButton) {
        audioRecording.rate = 2.0
        playButtons()
    }


    @IBAction func chipmunkButton(sender: UIButton) {

        playAudioWithVariablePitch(1000)

    }

    func playAudioWithVariablePitch(pitch: Float) {
        audioRecording.stop()
        audioEngine.stop()
        audioEngine.reset()

        var audioPlayerNode = AVAudioPlayerNode()
        audioEngine.attachNode(audioPlayerNode)

        var changePitchEffect = AVAudioUnitTimePitch()
        changePitchEffect.pitch = pitch
        audioEngine.attachNode(changePitchEffect)

        audioEngine.connect(audioPlayerNode, to: changePitchEffect, format: nil)
        audioEngine.connect(changePitchEffect, to: audioEngine.outputNode, format: nil)

        audioPlayerNode.scheduleFile(audioFile, atTime: nil, completionHandler: nil)
        audioEngine.startAndReturnError(nil)

        audioPlayerNode.play()


    }


    @IBAction func stopButton(sender: UIButton) {
       audioRecording.stop()

    }

    func playButtons() {
        audioRecording.stop()
        audioRecording.currentTime = 0
        audioRecording.play()

    }


}

【问题讨论】：

所以，当你调用scheduleFile时，audioFile参数就是nil。你在哪里设置的？
是的，您似乎没有在任何地方设置音频文件。

标签： ios swift null avaudioengine avaudioplayernode

【解决方案1】：

相当初级。只需阅读错误消息！你是说：

var audioFile:AVAudioFile!

这意味着audioFile 为零。好吧，在那之后你再也不会碰audioFile，所以它一开始是 nil 并且仍然是 nil。因此，当你到达这条线时，你会崩溃：

audioPlayerNode.scheduleFile(audioFile, atTime: nil, completionHandler: nil)

...正是因为audioFile 为零。

【讨论】：

【解决方案2】：

正如马特所说，audioFile 为 nil

因此，要解决此问题，您必须进行设置。查看代码，您应该使用

    audioFile = AVAudioFile(forReading: receivedAudio.filePathUrl, error: nil)

这将设置 audioFile 并且代码不会崩溃！

【讨论】：