使用 AFNetworking 解析 JSON

Question

我正在尝试从 Web api 捕获 JSON 请求。当我从服务器获得 JSON 格式的响应时，我以 NSData 格式而不是 NSDictionnary 接收它。我从本教程http://www.raywenderlich.com/30445/afnetworking-crash-course#（RESTful 类段落）中得到启发，以便通过 AFJSONRequestOperation 更改我的客户端的注册操作类来进行免费的 JSON 解析。但是，它不起作用，我仍然得到 NSData 格式的响应。

编辑：这是完整的错误消息：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFData objectForKey:]: unrecognized selector sent to instance 0x753aa00'

这是服务器的响应：

{"uid":"98545931","token":"98545931:176:ec0b862ba57fef88394950dd0cc41491"}

有人知道为什么不能自动解析吗？

AFHTTPClient *client = [[AFHTTPClient alloc] initWithBaseURL:baseurl];
//Here, we tell the AFHTTPClient that the server is responding to us in JSON format.
[client registerHTTPOperationClass:[AFJSONRequestOperation class]];

//Creating the dictionary containing the post parameters.
NSDictionary *params = [NSDictionary dictionaryWithObjectsAndKeys:username, @"username", password, @"password", nil];


//AUTHENTIFICATION. Retrieving token and uid by POST method.
[client postPath:@"/auth" parameters:params
         success:^(AFHTTPRequestOperation *operation, id responseObject)
{
    NSString *text = [[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding];
    NSLog(@"Response: %@", text);
    [responseField setText:text];
    self.jsonResponse = responseObject;

    //The NSJSONSerialization method to transform the NSData responseObject into a dictionnary does work
    self.jsonResponse = [NSJSONSerialization JSONObjectWithData:responseObject options:0 error:nil];

    //This NSLog makes the app crash with an unrecognized selector sent error
    NSLog(@"User ID: %@",[jsonResponse objectForKey:@"uid"]);
}
         failure:^(AFHTTPRequestOperation *operation, NSError *error)
{
             NSLog(@"%@", [error localizedDescription]);
             [responseField setText:[error localizedDescription]];
}];

Answer 1

只需使用 setDefaultHeader:value: 将默认 Header Accept 设置为 application/json 值，以便告诉 AFHTTPRequestOperation 它实际上是我们在回调中得到的 JSON。

Answer 2

您错过了对 setDefaultHeader:value: 的调用以将 Accept 标头设置为 application/json。没有这个，JSON 操作类将不会被使用，这意味着要退回到AFHTTPRequestOperation，它使用responseData 作为它的responseObject。