如果用户在swift iOS中点击两次，则取消NSURLSession

Question

使用根据此线程首选的NSURLSession即可。 How to make an HTTP request in Swift?

let url = NSURL(string: "http://www.stackoverflow.com") 

let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in 
    println(NSString(data: data, encoding: NSUTF8StringEncoding)) 
} 

task.resume() 

我唯一的问题是当用户点击两次，我想取消第一个请求。我已经尝试过task.cancel（），但是print语句仍然被执行（即在.cancel（）和NSDomainError之后）。我如何安全地取消这个请求（NSURLSessionDataTask），而不触发print语句，或者甚至可能？编辑： 只是要清楚。网址可能相同，我想取消第一个请求。

Answer 1

这就是我解决问题的方法。当执行task.cancel（）时，print语句不会被执行。似乎有点古怪检查一个字符串，所以如果任何人有更好的解决方案，我会接受一个。

let url = NSURL(string: "http://www.stackoverflow.com") 

let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in 
    if (error?.userInfo?["NSLocalizedDescription"] as? String) == "cancelled" 
      { 
       return 
      } 
    println(NSString(data: data, encoding: NSUTF8StringEncoding)) 
} 

task.resume() 

Answer 2

我希望这是你可以使用：

class ViewController: UIViewController , NSURLSessionDownloadDelegate { 

    var download : NSURLSessionDownloadTask? 
    var backgroundSession : NSURLSession? 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     let sessionConfiguration : NSURLSessionConfiguration = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("CustomBackgroundIdentifier") 
     backgroundSession = NSURLSession(configuration: sessionConfiguration, delegate: self, delegateQueue: NSOperationQueue.mainQueue()) 

     var btn = UIButton(frame: CGRectMake(0, 0, 100, 100)) 
     btn.backgroundColor = UIColor.redColor() 
     btn.addTarget(self, action: "startDownload", forControlEvents: UIControlEvents.TouchDown) 
     self.view.addSubview(btn) 

     var btn2 = UIButton(frame: CGRectMake(0, 120, 100, 100)) 
     btn2.backgroundColor = UIColor.blueColor() 
     btn2.addTarget(self, action: "cancelDownload", forControlEvents: UIControlEvents.TouchDown) 
     self.view.addSubview(btn2) 

    } 

    func startDownload() { 
     if download == nil { 
      if let url = NSURL(string: "http://www.stackoverflow.com") { 
       download = backgroundSession?.downloadTaskWithURL(url) 
       download?.resume() 
      } 
     } else { 
      resumeDownload() 
     } 
    } 

    func pauseDownload() { 
     if download != nil { 
      download?.suspend() 
     } 
    } 

    func resumeDownload() { 
     if download != nil { 
      download?.resume() 
     } 
    } 

    func cancelDownload() { 
     if download != nil { 
      download?.cancel() 
     } 
    } 

    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL) { 
     println("Session %@ download task %@ finished downloading to URL %@\n", 
     session, downloadTask, location) 
    } 

    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) { 
     println("downloaded: %i",totalBytesWritten) 
    } 
}