JSON ObjectiveC - Error

Question

Receiving the following error. I believe it has to do with the NSDictionary in the results of JSON array. I.e. NSDictionary within an NSDictionary maybe?

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

This is the JSON service when called. This is printed directly out of XCode but it looks clean to me.

    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;
    };
}

This is the code that invokes the JSON service.

 -(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]];

    }
}

It looks okay to me but maybe that is because I have been looking at it for hours.

Any ideas?

Google "unrecognized selector" and see what it means. Then learn how to get a proper exception stack trace so you can identify the failing line. — Hot Licks
– Hot Licks, Commented Nov 24, 2014 at 3:57
But one point is that there's no array in your JSON. Go to json.org and learn the JSON syntax. — Hot Licks
– Hot Licks, Commented Nov 24, 2014 at 3:58
Hi Hot Licks, Good point I hadn't thought of doing a search on how to get the "unrecognized selector". Still new at iOS but each day seems to be getting better thanks! — Jeremy
– Jeremy, Commented Nov 24, 2014 at 4:36
Always Google first. You learn a lot more that way than you do by coming here and asking someone to find your problem. — Hot Licks
– Hot Licks, Commented Nov 24, 2014 at 12:56

russell · Accepted Answer · 2014-11-24 04:49:16Z

2

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

These lines are wrong. currentMetarArray is a dictionary, not array, it contains string key & value, so you should access it like in following way-

NSDictionary *jsonDictionary = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error]; NSDictionary *weatherObservation = [jsonDictionary objectForKey:@"weatherObservation"];

then to get nCloud, use like NSString *nClouds = [weatherObservation objectForKey:@"clouds"];

answered Nov 24, 2014 at 4:49

russell

3,7969 gold badges46 silver badges57 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jeremy Over a year ago

Hi Russel, nailed it! Man both you and minh helped If I could give credits I would! I thought that having two dictionary's was the key just didn't know syntax how to do it (still newbie status). awesome sauce man.

Jeremy Over a year ago

totally helped. Both you and Minh. Thanks again guys!

Minh Quy · Accepted Answer · 2014-11-24 04:19:21Z

1

I go to your URL and get this message {"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}}

But you can try my code, it worked for me

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);
}

answered Nov 24, 2014 at 4:19

Minh Quy

6655 silver badges21 bronze badges

2 Comments

Jeremy Over a year ago

Hi Minh, sorry forgot to mention that I took out my users credentials in order for security. I do get back information. I'll review your suggestions now. thanks!

Jeremy Over a year ago

Okay I see what you have done. What you have done is correct. I just to work out each element within the returned value. i.e. temperature, wind speed etc. within the for loop.

esreli · Accepted Answer · 2014-11-24 04:57:28Z

The error thrown is the best clue for how you can fix this.

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

What this means is that you're thinking an object is a dictionary when in reality it isn't.

You can combat this using NSObject methods such as:

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

to see if the object will respond to the method you hope to send it

or

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

to determine if the object is a NSDictionary.

What's likely happening, though, is that you have an error in expectation with the Deserialized JSON Data.

Happy bug hunting!

Collectives™ on Stack Overflow

JSON ObjectiveC - Error

3 Answers 3

2 Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related