仅在状态正常时才下载Afnetworking下载文件

Question

我知道从这里使用Afnetworking下载文件的方法。我也在使用它。

How to download a file and save it to the documents directory with AFNetworking?

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"..."]];
AFHTTPRequestOperation *operation = [[[AFHTTPRequestOperation alloc] initWithRequest:request] autorelease];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"filename"];
operation.outputStream = [NSOutputStream outputStreamToFileAtPath:path append:NO];

[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSLog(@"Successfully downloaded file to %@", path);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", error);
}];

[operation start];

问题是它还下载了损坏的文件或状态不好的文件。

有些人要求检查operation.hasAcceptableStatusCode。

我该怎么办？