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iOS

Posted by PETRA LUTZ
PETRA LUTZ
2,922 Points

Program crashes - NSCFString objectForKeyedSubscript unrecognized selector sent to instance

When I run it, it crashes and gives this error:

NSCFString objectForKeyedSubscript unrecognized selector sent to instance.

I want to show markers on map from external JSON file, here below is my code:

    - (void)viewDidLoad
{
    [super viewDidLoad];
    [self.mapView setShowsUserLocation:YES];
    MKCoordinateRegion myRegion;
    CLLocationCoordinate2D center;
    center.longitude = 55.130761;
    center.latitude = 25.062718;
    //SPAN
    MKCoordinateSpan span;
    span.longitudeDelta = 0.40f;
    span.latitudeDelta = 0.40f;
    myRegion.span = span;
    myRegion.center = center;
    [self.mapView setRegion:myRegion animated:YES];
    //Loading Data from website
    NSURL *url = [NSURL URLWithString:@"http://example.com/api.php?user_id=2"];
    data = [NSData dataWithContentsOfURL:url];
    // parse the JSON into a NSArray
    NSError *error;
    NSArray *array = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
    if (error != nil)
    {
        ////
    }
    // a few variables to be used as we iterate through the array of results
    CLLocationCoordinate2D location;                         // coordinates of the annotation
    NSMutableArray *newAnnotations = [NSMutableArray array];
    MKPointAnnotation *newAnnotation;
    // iterate through the array, adding an annotation to our our array of new annotations
    for (NSDictionary *dictionary in array)
    {
        // retrieve latitude and longitude from the dictionary entry
        location.latitude = [dictionary[@"latitude"] doubleValue];
        location.longitude = [dictionary[@"longitude"] doubleValue];
        // create the annotation
        newAnnotation = [[MKPointAnnotation alloc] init];
        newAnnotation.title = dictionary[@"report_no"];
        newAnnotation.coordinate = location;
        [newAnnotations addObject:newAnnotation];
    }
    [self.mapView addAnnotations:newAnnotations];
}

Here is my JSON file how it looks like :

{
    reports: [
        {
            report_no: "3",
            user_id: "1",
            latitude: "25.085502",
            longitude: "55.158234"
        },
        {
            report_no: "4",
            user_id: "1",
            latitude: "24.931096",
            longitude: "55.018501"
        },
        {
            report_no: "6",
            user_id: "1",
            latitude: "24.993813",
            longitude: "55.094376",

        }
    ]
}

4 Answers

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

try setting an exception breakpoint so you can find out which line is causing the error.

PETRA LUTZ
PETRA LUTZ
2,922 Points

Thank you for your answer, I made what you've told me and here is the breakpoint :

location.latitude = [dictionary[@"latitude"] doubleValue];

But still I can not figure it out, any idea ?

PETRA LUTZ
PETRA LUTZ
2,922 Points
PETRA LUTZ
PETRA LUTZ
2,922 Points

Thank you for your answer, I made what you've told me and here is the breakpoint :

location.latitude = [dictionary[@"latitude"] doubleValue];

But still I can not figure it out, any idea ?

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

you have to access the latitude using

location.coordinate.latitude

not

location.latitude
PETRA LUTZ
PETRA LUTZ
2,922 Points

But, when I replace it, it gives an error saying that : no member named 'coordinate' in CLLocationCoordinate2D

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

sorry, i thought the location object was of type *CLLocation, not CLLocationCoordinate2d. My bad. hmm you are accessing the latitude correctly then. try using an NSLog on

[dictionary[@"latitude"] doubleValue]

and see what it outputs. There may be a problem with your dictionary if it doesnt output anything

PETRA LUTZ
PETRA LUTZ
2,922 Points

I tried NSLog using the following :

 NSString *digit = [dictionary[@"latitude"] doubleValue];
    NSLog(@"%@", digit);

But it gives error saying that : Initializing 'NSString' *__strong' with an expression of incompatible type double.

PETRA LUTZ
PETRA LUTZ
2,922 Points
PETRA LUTZ
PETRA LUTZ
2,922 Points

Any help ?