Question

收到以下错误。我相信它与JSON数组的结果中的NSDictionary有关。即NSDictionary中的NSDictionary可能吗？

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString objectForKey:]: unrecognized selector sent to instance 0x7f9298554560'

这是调用时的JSON服务。这是直接从XCode打印出来的，但它看起来很干净。

    Printing description of self->metArray:
{
    weatherObservation =     {
        ICAO = YBBN;
        clouds = "few clouds";
        cloudsCode = FEW;
        countryCode = AU;
        datetime = "2014-11-24 03:00:00";
        dewPoint = 20;
        elevation = 5;
        hectoPascAltimeter = 1014;
        humidity = 61;
        lat = "-27.38333333333333";
        lng = "153.1333333333333";
        observation = "YBBN 240300Z 02019KT 9999 FEW029 SCT250 28/20 Q1014";
        stationName = "Brisbane Airport M. O";
        temperature = 28;
        weatherCondition = "n/a";
        windDirection = 20;
        windSpeed = 19;
    };
}

这是调用JSON服务的代码。

 -(void)getMetar{

   // NSString *location = @"YBBN";
    NSString * const metarUrl =@"http://api.geonames.org/weatherIcaoJSON?ICAO=YBBN&username=demo";

    NSURL *url2 = [NSURL URLWithString:metarUrl];
    NSData *data2 = [NSData dataWithContentsOfURL:url2];

    metArray = [NSJSONSerialization JSONObjectWithData:data2 options:kNilOptions error:nil];

    //Create an NSDictionary for the weather data to be stored.
    NSDictionary *metarJson = [NSJSONSerialization JSONObjectWithData:data2 options:kNilOptions error:nil];

    //Loop through the JSON array
    NSArray *currentMetarArray = metarJson[@"weatherObservation"];

    //set up array and json call
    metarArray = [[NSMutableArray alloc]init];
   for (NSDictionary *metaritem in currentMetarArray)
    {
        //create our object
        NSString *nClouds = [metaritem objectForKey:@"clouds"];
        NSString *nObservation = [metaritem objectForKey:@"observation"];

        //Add the object to our animal array
        [metarArray addObject:[[metar alloc]initWithclouds:(nClouds) andobservation:nObservation]];

    }
}

对我来说看起来没问题，但也许是因为我已经看了几个小时了。

有什么想法吗？

Answer 1

 NSArray *currentMetarArray = metarJson[@"weatherObservation"];
 for (NSDictionary *metaritem in currentMetarArray)

这些行是错误的。 currentMetarArray是一个字典，不是数组，它包含字符串键＆amp;值，所以你应该像下面那样访问它 -

NSDictionary * jsonDictionary = [NSJSONSerialization JSONObjectWithData：数据选项：0错误：＆amp;错误]; NSDictionary * weatherObservation = [jsonDictionary objectForKey：@＆＃34; weatherObservation＆＃34;];

然后获得nCloud，使用类似 NSString * nClouds = [weatherObservation objectForKey：@＆＃34; clouds＆＃34;];

Answer 2

我转到您的网址并收到此消息{"status":{"message":"the daily limit of 30000 credits for demo has been exceeded. Please use an application specific account. Do not use the demo account for your application.","value":18}}

但你可以尝试我的代码，它对我有用

NSString *strUrl = @"http://api.geonames.org/weatherIcaoJSON?ICAO=YBBN&username=demo";
NSURL *url = [NSURL URLWithString:strUrl];
NSData *data = [NSData dataWithContentsOfURL:url];

NSError *error;

NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];

NSDictionary *weatherObservation = [json objectForKey:@"status"];

for (id key in weatherObservation) {
    id value = [weatherObservation objectForKey:key];

    NSLog(@"key = %@, value = %@", key, value);
}

Answer 3

抛出的错误是解决此问题的最佳线索。

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString objectForKey:]: unrecognized selector sent to instance 0x7f9298554560'

这意味着你认为一个对象是一个字典，而实际上却不是。

您可以使用NSObject方法解决此问题，例如：

[myObject respondsToSelector:(@selector(objectForKey:))]; // will return a boolean value.

查看对象是否会响应您希望发送的方法

或

[myObject isKindOfClass:[NSDictionary class]]; // will return a boolean value.

确定对象是否为NSDictionary。

但可能发生的情况是，您对反序列化的JSON数据的期望有误。

快乐的虫子狩猎！

JSON ObjectiveC - 错误

3 个答案: