Question

我是Objective-c的新手，我一直在努力解决这个问题。我有一个从服务器下载文件的类：

@interface DownloadManager ()
@property (nonatomic, strong) NSString *bytesWritten;

@end

@implementation DownloadManager

- (void)downloadTaskStart {
    NSURL  *url = [NSURL URLWithString:@"http://somehost.com/somefile.zip];
    NSMutableURLRequest *downloadRequest = [NSMutableURLRequest requestWithURL:url
                                                                   cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
                                                               timeoutInterval:60];
    NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *downloadSession = [NSURLSession sessionWithConfiguration:config
                                                                  delegate:self
                                                             delegateQueue:[NSOperationQueue mainQueue]];


    downloadTask = [downloadSession downloadTaskWithRequest:downloadRequest];
    startTime = [NSDate timeIntervalSinceReferenceDate];
    [downloadTask resume];

}

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
    if (error) {
        NSLog(@"Error when download: %@", error);
    } 

    //do something?
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {
    //do something?
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {            
    self.bytesWritten = [@(totalBytesWritten) stringValue];
}

@end

我想要做的是当我从另一个类向-(void)downloadTaskStart发送消息然后获取bytesWritten值（我使用单身）时，它将在任务完成后返回值（或者错误与否），而不是在第一个毫秒时的值。感谢您的帮助！

Answer 1

您可以使用

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

NSURLSession的方法，因为它将在任务完成时调用，如果出现错误并传递值，请使用Delegates或NSNotification

在URLSession中完成任务后返回值

1 个答案: