关于AFNetWorking 下载进度 显示"The operation couldn’t be completed. Is a directory" 的bug处理

NSURL *URL = [NSURL URLWithString:@"http://cdn.sencha.com/ext/gpl/ext-4.2.1-gpl.zip"];    NSURLRequest *request = [NSURLRequest requestWithURL:URL];        //下载请求    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];    //正确的下载路径 [self getImagePath:@"3.zip"]        //错误的路径//    NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,  NSUserDomainMask, YES);//    NSString *docPath = [path objectAtIndex:0];        operation.outputStream = [NSOutputStream outputStreamToFileAtPath:[self getImagePath:@"3.zip"] append:YES];    //下载进度回调    [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {        //下载进度        float progress = ((float)totalBytesRead) / (totalBytesExpectedToRead);        NSLog(@"%f",progress);    }];    //成功和失败回调    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {        NSLog(@"ok");    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {        NSLog(@"%@",error);    }];        [operation start];

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">http://stackoverflow.com/questions/14248757/error-domain-nscocoaerrordomain-code-512-the-operation-couldn-t-be-completed-th</span>