Downloading an Object Body

class delegate :NSObject, URLSessionDataDelegate, URLSessionDownloadDelegate{

  func downloadObjectBody(){
    // Check if a KiiUser is logged in.
    if KiiUser.current() == nil{
      return
    }
    // Instantiate the target KiiObject.
    let object = KiiObject(uri: "Set the URI of an existing KiiObject here")!

    // Prepare a URLSession object to download the object body in the background.
    let downloadRequest = object!.generateDownloadRequest()!
    let uuidStr = UUID().uuidString
    let randomSessionIdentifier = uuidStr.lowercased()
    let sessionConfig : URLSessionConfiguration
    sessionConfig = URLSessionConfiguration.background(withIdentifier: randomSessionIdentifier)
    sessionConfig.allowsCellularAccess = true
    let session = URLSession(configuration: sessionConfig, delegate: self, delegateQueue: OperationQueue.main)

    // Create a download task.
    let downloadTask = session.downloadTask(with: downloadRequest)

    // Start or resume the task.
    downloadTask.resume()
  }

  @objc fileprivate func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
    // The download is in progress.
    print("Progress : \(Float(totalBytesWritten / totalBytesExpectedToWrite))")
  }

  @objc fileprivate func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
    // Note: The file will be downloaded in a temporary area. Move the downloaded file to a persistent area if needed.

    // Specify the file destination.
    let targetDirectory : NSString = (NSHomeDirectory() as NSString).appendingPathComponent("Documents") as NSString
    let downloadFilePathStr = targetDirectory.appendingPathComponent("sample.mp4")
    let downloadFilePath = URL(fileURLWithPath: downloadFilePathStr)
    let fileManager = FileManager.default

    do{
      try fileManager.moveItem(at: location, to: downloadFilePath)
    }catch (let error){
      print("File move is failed \(error)")
      return
    }
    print("Download succeeded")
  }

  @objc fileprivate func urlSession(_ session : URLSession, task: URLSessionTask, didCompleteWithError error: Error? ){
    if error != nil {
      // Handle the error.
      print("Background transfer is failed")
      return
    }
    // Check the HTTP status code.
    let response = task.response as! HTTPURLResponse
    if response.statusCode >= 300 {
      print("Background transfer is failed, status code: \(response.statusCode)")
      return
    }
    print("Background transfer succeeded")
  }
}

- (void)downloadObjectBody {
  // Check if a KiiUser is logged in.
  if ([KiiUser currentUser] == nil) {
    return;
  }
  // Instantiate the target KiiObject.
  KiiObject *object = [KiiObject objectWithURI:@"Set the URI of an existing KiiObject here"];

  // Prepare an NSURLSession object to download the object body in the background.
  NSURLRequest *downloadRequest = [object generateDownloadRequest];
  CFUUIDRef uuid = CFUUIDCreate(kCFAllocatorDefault);
  NSString *uuidStr = (__bridge_transfer NSString *) CFUUIDCreateString(kCFAllocatorDefault, uuid);
  CFRelease(uuid);
  NSString *randomSessionIdentifier = [uuidStr lowercaseString];
  NSURLSessionConfiguration *sessionConfig;
  sessionConfig = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:randomSessionIdentifier];
  sessionConfig.allowsCellularAccess = YES;
  NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig
                                                        delegate:self
                                                   delegateQueue:[NSOperationQueue mainQueue]];

  // Create a download task.
  NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:downloadRequest];

  // Start or resume the task.
  [downloadTask resume];
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
  // The download is in progress.
  NSLog(@"Progress : %f", (float) totalBytesWritten / totalBytesExpectedToWrite);
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {
  // Note: The file will be downloaded in a temporary area. Move the downloaded file to a persistent area if needed.

  // Specify the file destination.
  NSString *targetDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
  NSString *downloadFilePathStr = [targetDirectory stringByAppendingPathComponent:@"sample.mp4"];
  NSURL *downloadFilePath = [NSURL fileURLWithPath:downloadFilePathStr];
  NSFileManager *fileManager = [NSFileManager defaultManager];
  NSError *moveError = nil;
  [fileManager moveItemAtURL:location toURL:downloadFilePath error:&moveError];

  if (moveError != nil) {
    // Handle the error.
    NSLog(@"File move is failed");
    return;
  }
}

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
  if (error != nil) {
    // Handle the error.
    NSLog(@"Background transfer is failed");
    return;
  }
  // Check the HTTP status code.
  NSHTTPURLResponse *response = (NSHTTPURLResponse *)task.response;
  if ([response statusCode] >= 300) {
    NSLog(@"Background transfer is failed, status code: %ld", (long)[response statusCode]);
    return;
  }
  NSLog(@"Background transfer succeeded");
}