NSURLSessionDownloadDelegate 协议的错误信息

Question

我实际上正在处理 download/upload 文件并跟踪进度。它运作良好。但是，我只是想知道如果出现问题怎么办，而且我在该委托中没有看到任何处理错误的方法。以下是 NSURLSessionDownloadDelegate:

中的方法

/*
 * Messages related to the operation of a task that writes data to a
 * file and notifies the delegate upon completion.
 */
@protocol NSURLSessionDownloadDelegate <NSURLSessionTaskDelegate>

/* Sent when a download task that has completed a download.  The delegate should 
 * copy or move the file at the given location to a new location as it will be 
 * removed when the delegate message returns. URLSession:task:didCompleteWithError: will
 * still be called.
 */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
                              didFinishDownloadingToURL:(NSURL *)location;

@optional
/* Sent periodically to notify the delegate of download progress. */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
                                           didWriteData:(int64_t)bytesWritten
                                      totalBytesWritten:(int64_t)totalBytesWritten
                              totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite;

/* Sent when a download has been resumed. If a download failed with an
 * error, the -userInfo dictionary of the error will contain an
 * NSURLSessionDownloadTaskResumeData key, whose value is the resume
 * data. 
 */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
                                      didResumeAtOffset:(int64_t)fileOffset
                                     expectedTotalBytes:(int64_t)expectedTotalBytes;

@end

只是想知道如何返回错误消息，谢谢。

Answer 1

让您的代表遵守 NSURLSessionTaskDelegate 并实施：

- (void)URLSession:(NSURLSession *)session
              task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error

EDIT 进一步澄清，请参阅 the doc for NSURLSessionDownloadDelegate，请注意靠近顶部的地方：

In addition to these methods, be sure to implement the methods in the NSURLSessionTaskDelegate and NSURLSessionDelegate protocols to handle events common to all task types and session-level events, respectively.

想法是 url 会话的委托可以符合任何这些协议。您正在寻找的方法，即指示错误的方法，只是比下载任务更通用，它可能发生在任何类型的会话任务上，因此他们将其放在更抽象的协议中。

NSURLSessionDownloadDelegate 协议的错误信息

Error message on NSURLSessionDownloadDelegate Protocol

ios

objective-c

nsurlsessiondownloadtask