下载下一个音频时，获取已经下载的音频的URL

Question

我使用urlsession委托下载2个音频。在下载第一个音频时可以正常工作，但是在下载第二个音频时，则音频会从缓存中移到缓存中，同时从缓存移至内部存储文件时，错误音频已经退出。

此方法用于下载音频。

func downloadPracticeTest(index : Int) {

   if !Utile.isInternetAvailable() {

   self.showAlert(title: Utile.getLocalizedString(key: Constants.ApiErrorTitle.noInternetTitle), message: Utile.getLocalizedString(key: Constants.ApiErrorMessage.errorNoInternetMediaDownload))
        return
    }

   if isDownloadViewShown == false {
        self.showDownloadView()
        isDownloadViewShown = true
   }
   let arrayAudioUrl = getTheAudioUrlList()
   let urlObject = URL(string: arrayAudioUrl[index])
   let audioPath = Utile.getDocumentDirectoryForAudio()
   self.destinationUrl = nil
   self.destinationUrlString = nil
   self.destinationUrlString = (audioPath.appendingPathComponent((urlObject?.lastPathComponent)!)).description
   self.destinationUrl = audioPath.appendingPathComponent((urlObject?.lastPathComponent)!)
   print(self.destinationUrl as Any)

   //Check Audio already exist or not
   if self.fileManager.fileExists(atPath: self.destinationUrl?.path ?? "") {
   print("Exist")
   let arrayAudioUrl = self.getTheAudioUrlList()

   //if all audio is not downloaded
   if (self.audioIndex < arrayAudioUrl.count) {
   self.destinationUrl = nil
   self.destinationUrlString = nil
   self.destinationUrlString = (audioPath.appendingPathComponent((urlObject?.lastPathComponent)!)).description
   self.destinationUrl = audioPath.appendingPathComponent((urlObject?.lastPathComponent)!)
   self.downlProgress = self.downlProgress + Double((100/arrayAudioUrl.count)*self.audioIndex)
   self.downloadPracticeTest(index: self.audioIndex)
   self.audioIndex = self.audioIndex + 1
   //if all audio is downloaded
   } else {
   self.startTestAfterAudioDownloaded()
   }
   //if audio not present
   } else {
   self.destinationUrl = nil
   self.destinationUrlString = nil
   self.destinationUrlString = (audioPath.appendingPathComponent((urlObject?.lastPathComponent)!)).description
   self.destinationUrl = audioPath.appendingPathComponent((urlObject?.lastPathComponent)!)

   self.downlProgress = self.downlProgress + Double(25*self.audioIndex)
   self.downloadsSession.downloadTask(with: URL(string: arrayAudioUrl[index])!).resume()
       }         
   }

委托方法是这个

 func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
    print("success")

    let arrayAudioUrl = getTheAudioUrlList()
    if (audioIndex < arrayAudioUrl.count) {
    let fileManager = FileManager.default
    if fileManager.fileExists(atPath: location.path) {
    print("Exixt")
    do {
    if let url =  destinationUrlString {
    // after downloading your file you need to move it to your destination url
    try FileManager.default.moveItem(at: location, to: URL(string: url)!)
    //delete the downloaded file from the temp folder after moving to new location
    Utile.deleteFile(path: location)
    }
    print("File moved to documents folder")
    } catch  {
    print("\(error)")
    }
    }