Question

我有以下代码已经工作了几个月，并且刚刚开始间歇性地破解。

我正在改变它被调用的方式，所以它并不完全不足为奇，但症状令我感到困惑。某些请求正在下载的临时文件似乎在读取数据之前被删除。

我有关于文件，它的位置的属性，并且当在模拟器中运行时，我甚至确认该文件包含正确的数据，而在断点中。但是，只要调用[NSData dataWithContentsOfFile:[location path]]或[NSData dataWithContentsOfURL:location]，文件就会从文件系统中删除，如果我使用传入NSError的方法，我得到的错误是Error Domain=NSCocoaErrorDomain Code=260 "The operation couldn’t be completed.

我的代码：

- (void)makeSoapRequest:(NSURL *)url soapRequest:(NSString *)soapRequest completionBlock:(void (^)(NSData *xmlToParse, int error))completionBlock attemptNumber:(int)attemptNumber
{
    NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfiguration delegate:nil delegateQueue:nil];
    NSData *bodyData = [soapRequest dataUsingEncoding:NSUTF8StringEncoding];

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc]initWithURL:url];
    [request setHTTPMethod:@"POST"];
    [request addValue:@"text/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"];
    [request addValue:@"" forHTTPHeaderField:@"SOAPAction"];
    [request addValue:[NSString stringWithFormat:@"%d",(int)[bodyData length]] forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody:bodyData];

    NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {
    if (!(location == nil))
    {
        dispatch_async(dispatch_get_main_queue(), ^{
            if (error)
            {
                NSLog(@"nsurl error was: %@", error);
            }
            else
            {
                NSError* errorObj;
                NSString *path = [location path];

                NSDictionary* attribs = [[NSFileManager defaultManager] attributesOfItemAtPath:path error:&errorObj];
                NSData *xmlData= [NSData dataWithContentsOfFile:path options:NSDataReadingMappedIfSafe error:&errorObj];
                if (errorObj != nil) {
                    NSLog(@"Attributes of file: %@", attribs);
                    NSLog(@"Error reading the downloaded data, error was: %@", errorObj);
                }
                completionBlock(xmlData, 0);
                return;
            }
        });
    }
    else
    {
        if (error)
        {
            dispatch_async(dispatch_get_main_queue(), ^{
                completionBlock(nil,-1);
            });
        }
        else
        {
            dispatch_async(dispatch_get_main_queue(), ^{
                completionBlock(nil,-1);
            });
        }
    }
}];
[downloadTask resume];
}

我的属性打印输出：

Attributes of file: {
NSFileCreationDate = "2016-11-23 13:15:00 +0000";
NSFileExtensionHidden = 0;
NSFileGroupOwnerAccountID = 501;
NSFileGroupOwnerAccountName = mobile;
NSFileModificationDate = "2016-11-23 13:15:00 +0000";
NSFileOwnerAccountID = 501;
NSFileOwnerAccountName = mobile;
NSFilePosixPermissions = 384;
NSFileReferenceCount = 1;
NSFileSize = 947;
NSFileSystemFileNumber = 534146;
NSFileSystemNumber = 16777218;
NSFileType = NSFileTypeRegular;
}

错误日志：

2016-11-23 13:27:43.285 GCMMobile[2780:829109] Error reading the downloaded data, error was: Error Domain=NSCocoaErrorDomain Code=260 "The operation couldn’t be completed. (Cocoa error 260.)" UserInfo=0x1704605c0 {NSFilePath=/private/var/mobile/Containers/Data/Application/BF6BE574-AA1A-492E-A1DD-04334F33E2D7/tmp/CFNetworkDownload_VHyKp6.tmp, NSUnderlyingError=0x17024ce10 "The operation couldn’t be completed. No such file or directory"}

任何最感谢的帮助...

Answer 1

问题是您在移动或打开下载的文件之前从NSURLSessionDownloadTask完成处理程序返回。正如documentation所述：

您必须在完成之前移动此文件或将其打开以供阅读处理程序返回否则，文件将被删除，数据将丢失。

通过调度到主队列并返回，您将文件读取代码推迟到将来的某个无限期。您应该在完成处理程序本身中移动或打开文件，然后才会调度到另一个队列以进行后续处理。

在读取内容之前删除了NSURLSessionDownloadTask文件

1 个答案: