Ios 常数'；错误'；在初始化之前使用_Ios_Swift_Error Handling_Constants_Avaudiorecorder

Ios 常数'；错误'；在初始化之前使用

ios swift error-handling

Ios 常数'；错误'；在初始化之前使用,ios,swift,error-handling,constants,avaudiorecorder,Ios,Swift,Error Handling,Constants,Avaudiorecorder,我检测到麦克风的响声，并用它来触发一个动画，我得到了这个错误信息。“初始化前使用的常量“错误”。这是我的代码： override func viewDidLoad() { super.viewDidLoad() //make an AudioSession, set it to PlayAndRecord and make it active let audioSession:AVAudioSession = AVAudioSession.sharedInsta

我检测到麦克风的响声，并用它来触发一个动画，我得到了这个错误信息。“初始化前使用的常量“错误”。这是我的代码：

    override func viewDidLoad() {
    super.viewDidLoad()

    //make an AudioSession, set it to PlayAndRecord and make it active
    let audioSession:AVAudioSession = AVAudioSession.sharedInstance()
    try! audioSession.setCategory(AVAudioSessionCategoryRecord)
    try! audioSession.setActive(true)

    //set up the URL for the audio file
    let documents: AnyObject = NSSearchPathForDirectoriesInDomains( FileManager.SearchPathDirectory.documentDirectory,  FileManager.SearchPathDomainMask.userDomainMask, true)[0] as AnyObject
    let str = (documents as! NSString).appending("recordTest.caf")
    NSURL.fileURL(withPath: str as String)


    // make a dictionary to hold the recording settings so we can instantiate our AVAudioRecorder
    let recordSettings: [NSObject : AnyObject] = [AVFormatIDKey as NSObject:kAudioFormatAppleIMA4 as AnyObject,
                                                  AVSampleRateKey as NSObject:44100.0 as AnyObject,
                                                  AVNumberOfChannelsKey as NSObject:2 as AnyObject,AVEncoderBitRateKey as NSObject:12800 as AnyObject,
                                                  AVLinearPCMBitDepthKey as NSObject:16 as AnyObject,
                                                  AVEncoderAudioQualityKey as NSObject:AVAudioQuality.max.rawValue as AnyObject

    ]

    //declare a variable to store the returned error if we have a problem instantiating our AVAudioRecorder
    let error: NSError?

    //Instantiate an AVAudioRecorder
    recorder = try! AVAudioRecorder(url: documents as! URL, settings: recordSettings as! [String : Any])

    //If there's an error, print it - otherwise, run prepareToRecord and meteringEnabled to turn on metering (must be run in that order)
    if let e = error {
        print(e.localizedDescription)
    } else {
        recorder.prepareToRecord()
        recorder.isMeteringEnabled = true

        //start recording
        recorder.record()

        //instantiate a timer to be called with whatever frequency we want to grab metering values
        self.levelTimer = Timer.scheduledTimer(timeInterval: 0.02, target: self, selector: #selector(ViewController.levelTimerCallback), userInfo: nil, repeats: true)

    }

}

//selector/function is called every time our timer (levelTime) fires
func levelTimerCallback() {
    //update meters
    recorder.updateMeters()

    //print to the console if we are beyond a threshold value
    if recorder.averagePower(forChannel: 0) > -7 {
        print("Mic Blow Detected ")
        print(recorder.averagePower(forChannel: 0))
        isAnimating = false
    } else {
        isAnimating = true
    }
}

这句话似乎也迫使应用程序退出，显然这就是问题所在，但我是Xcode新手，无法发现我做错了什么，如果有人对我应该做什么也有想法，那就太好了

recorder = try! AVAudioRecorder(url: documents as! URL, settings: recordSettings as! [String : Any])

提前谢谢

您没有可以在声明点和使用点之间设置

error

值的代码。对于可能采用新值的错误，必须将其传递给

AVAudioRecorder

的构造函数。您可以使用以下命令初始化错误：

let错误：错误？=无

但这同样是无足轻重的，因为它的值不可能改变（它是一个

let

变量），即使它是一个var，在声明它和在

if let

构造中使用它之间，它也不会传递给任何代码

您正在崩溃，因为您告诉系统您要创建AVAudioRecorder，但它永远不会失败（即

尝试！

）。您更可能希望执行以下操作：

let documentSearchPaths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let documentsDir = documentSearchPaths[0] as NSString
let recordingFilePath = documentsDir.appendingPathComponent("recordTest.caf")
let recordingFileURL = NSURL.fileURL(withPath: recordingFilePath)

var recorder : AVAudioRecorder?
do{
    let audioSession = AVAudioSession.sharedInstance()
    try audioSession.setCategory(AVAudioSessionCategoryRecord)
    try audioSession.setActive(true)

    // make a dictionary to hold the recording settings so we can instantiate our AVAudioRecorder
    let recordSettings: [String : Any] = [AVFormatIDKey : kAudioFormatAppleIMA4,
                                          AVSampleRateKey : NSNumber(value: 44100.0),
                                          AVNumberOfChannelsKey : NSNumber(value: 2),
                                          AVEncoderBitRateKey : NSNumber(value: 12800),
                                          AVLinearPCMBitDepthKey : NSNumber(value: 16),
                                          AVEncoderAudioQualityKey :NSNumber(value: AVAudioQuality.max.rawValue)
    ]

    recorder = try AVAudioRecorder(url: recordingFileURL, settings: recordSettings)
} catch let audio_error as NSError {
    print("Setting up the audio recording failed with error \(audio_error)")
}

if let recorder = recorder {
    recorder.prepareToRecord()
    recorder.isMeteringEnabled = true

    //start recording
    recorder.record()

    //etc...
}