我在使用 [NSURLConnection sendAsynchronousRequest: queue: completionHandler:] 时遇到了一些严重的问题。我正在使用休息代理登录和验证用户。下面是我用来登录的如下图:

    //Display the progress HUB
    [SVProgressHUD showWithStatus:@"Signing Up..." maskType:SVProgressHUDMaskTypeClear];

    NSError *error;
    [self setUserCredentials];

    //assign the parentView controller to the sender and email to the local class variables
    parentView = sender;
    userEmail = email;

    // create json object for a users session
    NSDictionary* session = [NSDictionary dictionaryWithObjectsAndKeys:
                             email, @"email",
                             password, @"password",
                             [NSDictionary dictionaryWithObjectsAndKeys:
                              [[UIDevice currentDevice] model], @"device",
                              [[UIDevice currentDevice] identifierForVendor].UUIDString, @"device_id",
                              @"APNS", @"push_to",
                              [[NSUserDefaults standardUserDefaults] stringForKey:@"push_id"], @"push_id",
                              nil],
                             @"mession",
                             nil];

    NSData *jsonSession = [NSJSONSerialization dataWithJSONObject:session options:NSJSONWritingPrettyPrinted error:&error];
    NSString *url = [NSString stringWithFormat:@"%@api/v1/messions.json", CoffeeURL];

    NSLog(@"URL: %@", url);

    NSURL *URL = [NSURL URLWithString:url];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL
                                                           cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                       timeoutInterval:30.0];

    [request setHTTPMethod:@"POST"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [request setValue:[NSString stringWithFormat:@"%d", [jsonSession length]] forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody:jsonSession];

    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

        NSLog(@"Length: %d", data.length);

        if (error == nil)
        {
            //if no error ocours set the user defualts and create the mession and log into the app
            NSString *dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
            NSDictionary *JSONResponse = [NSJSONSerialization JSONObjectWithData:[dataString dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingMutableContainers error: &error];

            NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;

            NSLog(@"JSON: %@", JSONResponse);
            NSLog(@"Response: %d", httpResponse.statusCode);

            if (JSONResponse != nil && httpResponse.statusCode == 200)
            {
                [self setUserDefualts:password sessionToUse:JSONResponse deckController:viewDeck sender:sender];
            }

            [SVProgressHUD dismiss];
        }
        else
        {
            NSLog(@"Error: %@", error);

            //Dismiss progress HUB here and inform user that an internal error has occured
            [SVProgressHUD dismiss];
            NSString *errorString = @"Sorry, an error has occoured while connecting to the Coffee server.";
            UIAlertView *errorAlertView = [[UIAlertView alloc] initWithTitle:@"Error" message:errorString delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
            [errorAlertView show];
        }
    }];

当我使用有效的用户凭据登录时，此代码可以正常工作。当我使用无效凭据时，服务器会向 iOS 客户端发送一个 401 和一个空 JSON 对象。这应该返回一个 error = nil 和一个状态代码 401 以及一个有效的非空响应对象。由于某种原因返回错误并且响应为 nil:

Error: Error Domain=NSURLErrorDomain Code=-1012 "The operation couldn’t be completed.
(NSURLErrorDomain error -1012.)" UserInfo=0x1cd53b50 
{NSErrorFailingURLKey=http://192.155.94.183/api/v1/messions.json, 
NSErrorFailingURLStringKey=http://192.155.94.183/api/v1/messions.json, 
NSUnderlyingError=0x1cdc2b10 "The operation couldn’t be completed. (kCFErrorDomainCFNetwork
 error -1012.)"}

这让我很难区分发送请求时发生的错误和用户凭据与后端不匹配时服务器生成的 401 错误。当我尝试创建和处理请求时:

NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[connection start];

和 NSURLDelegate:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"Called Outside!");

    NSDictionary *jsonSession;
    NSUserDefaults *userInfo = [NSUserDefaults standardUserDefaults];
    NSLog(@"Succeeded! Received %d bytes of data", [responseData length]);
    recievedResponse = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];

    NSError *err = nil;
    jsonSession = [NSJSONSerialization JSONObjectWithData:[recievedResponse dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingMutableContainers error:&err];

    if ([connection.originalRequest.URL isEqual:[NSURL URLWithString:[NSString stringWithFormat:@"%@api/v1/messions.json", CoffeeURL]]])
    {
        NSLog(@"Status: %d", httpResponse.statusCode);
        NSLog(@"JSON: %@", jsonSession);
        NSLog(@"Called Inside!");
    }
}

返回的响应有效，当用户输入无效凭据时，不会抛出错误并且状态代码等于 401。为什么这适用于 (void)connectionDidFinishLoading:(NSURLConnection *)connection 但不适用于 [NSURLConnection sendAsynchronousRequest: queue: completionHandler:]？

最佳答案

当 URL 处理系统收到错误 HTTP 状态代码(即不是 2xx)时，不要依赖于未生成的错误。

相反，使用返回的 response 可以访问 HTTP 状态代码(在运行时检查类并转换为 NSHTTPURLResponse 以便您可以访问 statusCode )。

关于sendsynchronousRequest 的 IOS 问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19824008/