在这种情况下，我认为您应该使用NSURLSession.sharedSession（）。dataTaskWithURL从链接中进行多次下载，但要保持下载操作异步。您需要向其添加一个回调块。您应该执行以下操作：
let documentsUrl = NSFileManager.defaultManager().URLsForDirectory(.documentDirectory, inDomains: .UserDomainMask).first as NSURLlet musicArray:[String] = ["http://freetone.org/ring/stan/iPhone_5-Alarm.mp3","http://freetone.org/ring/stan2/Samsung_Galaxy_S4-SMS.mp3","https://www.sounddogs.com/sound-effects/25/mp3/235178_SOUNDDOGS__al.mp3"]var musicUrls:[NSURL!]!// create a function to start the audio data downloadfunc getAudioDataFromUrl(audioUrl:NSURL, completion: ((data: NSData?) -> Void)) { NSURLSession.sharedSession().dataTaskWithURL(audioUrl) { (data, response, error) in completion(data: data) }.resume()}// create another function to save the audio datafunc saveAudioData(audio:NSData, destination:NSURL) -> Bool { if audio.writeToURL(destination, atomically: true) { println("The file "(destination.lastPathComponent!.stringByDeletingPathExtension)" was successfully saved.") return true } return false}// just convert your links to Urlsfunc linksToUrls(){ musicUrls = musicArray .map() { NSURL(string: $0) } .filter() { $0 != nil }}// create a loop to start downloading your urlsfunc startDownloadingUrls(){ for url in musicUrls { let destinationUrl = documentsUrl.URLByAppendingPathComponent(url.lastPathComponent!) if NSFileManager().fileExistsAtPath(destinationUrl.path!) { println("The file "(destinationUrl.lastPathComponent!.stringByDeletingPathExtension)" already exists at path.") } else { println("Started downloading "(url.lastPathComponent!.stringByDeletingPathExtension)".") getAudioDataFromUrl(url) { data in dispatch_async(dispatch_get_main_queue()) { println("Finished downloading "(url.lastPathComponent!.stringByDeletingPathExtension)".") println("Started saving "(url.lastPathComponent!.stringByDeletingPathExtension)".") if self.saveAudioData(data!, destination: self.documentsUrl.URLByAppendingPathComponent(url.lastPathComponent!) ) { // do what ever if writeToURL was successful } else { println("The File "(url.lastPathComponent!.stringByDeletingPathExtension)" was not saved.") } } } } }}override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. println("Begin of pre") linksToUrls() startDownloadingUrls() println("End of pre")}
