Why does my iOS app crash with JSON? - ios

Question

I'm trying to acces my JSON in Objective-C from a higher scope. But it keeps crashing and I have no idea why.
The following code works:
- (void)fetchedData:(NSData *)responseData {
NSError* error;
NSDictionary* json = [NSJSONSerialization
JSONOnkectWithData: responseData
options:kNilOptions
error:&error];
NSArray* nameAndPlace = [[json objectForKey:#"objects"] objectForKey:#"havens"];
//NSArray* productArray = [[json objectForKey:#"objects"] objectForKey:#"products"];
NSLog(#"FROM ---> %#", nameAndPlace);
for (NSDictionary *mapPointLoop in nameAndPlace) {
NSString * name = [mapPointLoop objectForKey:#"name"];
NSString * longitudeGet = [mapPointLoop objectForKey:#"longitude"];
NSString * latitudeGet = [mapPointLoop objectForKey:#"latitude"];
myAnnotation *annotation1 = [[myAnnotation alloc] init];
CLLocationCoordinate2D coordinate1;
coordinate1.longitude = longitude;
coordinate1.latitude = latitude;
annotation1.coordinate = coordinate1;
annotation1.title = name;
[mainMap addAnnotation:annotation1];
//NSLog(#"FROM ---> %#", mapPointLoop);
}
}
But when I use this it crashes:
- (void)fetchedData:(NSData *)responseData {
NSError* error;
NSDictionary* json = [NSJSONSerialization
JSONObjectWithData:responseData
options:kNilOptions
error:&error];
NSArray* nameAndPlace = [json objectForKey:#"objects"];
//NSArray* productArray = [[json objectForKey:#"objects"] objectForKey:#"products"];
NSLog(#"FROM -> %#", nameAndP1ace);
for (NSDictionary *mapPointLoop in nameAndPlace) {
NSString * name = [[mapPointLoop objectForKey:#"havens"] objectForKey:#"name"];
NSNumber * longitudeGet = [mapPointLoop objectForKey:#"longitude"];
NSNumber * latitudeGet = [mapPointLoop objectForKey:#"latitude"];
float latitude = [latitudeGet floatvalue];
float longitude = [longitudeGet floatvalue];
myAnnotation *annotation1 = [[myAnnotation alloc] init];
CLLocationCoordinate2D coordinate1;
coordinate1.longitude = longitude;
coordinate1.latitude = latitude;
annotation1.coordinate = coordinate1
annotation1.title = name;
[mainMap addAnnotation:annotation1];
//NSLog(#"FROM -> %#", mapPointLoop):
}
}
It crashes with the error...
2014-05-20 17:49:57.709 labelAPortTest[5556:60b] * Terminating app
due to uncaught exception 'NSInvalidArgumentException', reason:
'-[__NSCFString objectForKey:]: unrecognized selector sent to instance
0x1172426b0'

Answer 1

It crash because when you take the name:
NSString *name = [[mapPointLoop objectForKey:#"havnes"] objectForKey:#"name"];
this:
[mapPointLoop objectForKey:#"havens"]
is an NSArray and not an NSDictionary with the key name.
In fact in your first code you take the objectForKey:#"objects"] objectForKey:#"havens]"
so you have this situation:
NSDictionary ~> objects ~> NSDictionary ~> havens ~> NSArray (of NSDictionary)
then you go to through a for cycle getting 1 to 1 the NSDictionary in the NSArray.
Second case (that crash):
NSDictionary ~> objects ~> NSDictionary
but your are putting that in an NSArray going again with the for cycle..on an NSDictionary.

Answer 2

But it keeps crashing and I have no idea why.
The reason is right here:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString objectForKey:]: unrecognized selector sent to instance 0x1172426b0'
You have an uncaught exception. Furthermore, you have some information about what that exception is, namely that you're sending the objectForKey: message to an object that doesn't implement it.
The first thing you should do is to set a breakpoint for all exceptions:
That'll cause the debugger to stop as soon as the exception is thrown instead of waiting until the app exits, which will give you a lot more context. You should be able to see which object is getting the unknown message. If that doesn't make the problem completely clear, set a breakpoint a line or two before the exception happens and step through the code a line at a time until you find the problem.