Question

Goal: Combine all NSDictionaries returned with one common key value ‘delay’ into a single NSMutablearry that I can use to compare the results (true or false) to place either a green or red pin on a map.
This code brings back the airport data in JSON that I convert to a dictionary of the requested airports. There are a number of keys, but in this part of the code I am only interested in one – ‘delay’ that I want to combine into one NSMutablearry.
Because I can only request one airport at a time, it brings back each requested airport individually and I get 9 sets of data. What I want is the 9 delay keys all in one array for the 9 different airports.

`- (void)configureData
{

self.airportCodes = [[NSArray alloc] initWithObjects:

                     @"ATL",
                     @"BOS",
                     @"BWI",
                     @"CLT",
                     @"CVG",
                     @"DEN",
                     @"EWR",
                     @"ORD",
                     @"SFO",
                     nil];

NSUInteger airportCount = self.airportCodes.count;


for(int i=0; i < airportCount;i++){

    NSURL *url = [self urlWithSearchText:[self.airportCodes objectAtIndex: i]];
    NSString *jsonString = [self performAirportRequestWithURL:url];
    if (jsonString == nil) {
        [self showNetworkError];

    }


    NSDictionary *dictionary = [self parseJSON:jsonString];
    if (dictionary == nil) {
        [self showNetworkError];
    }

    self.airportDelays = [[NSMutableArray alloc] initWithCapacity:9];


    [self parseDelay:dictionary];

    //NSLog(@"AP Delays %@",self.airportDelays);
} 

return;
}


-  (void)parseDelay:(NSDictionary *)dictionary
{


//self.delay = [dictionary objectForKey:@"delay"];
[self.airportDelays addObject:dictionary];



NSLog(@"AP Delays %@",self.airportDelays);

return;
}

- (NSURL *)urlWithSearchText:(NSString *)searchText
{
NSString *escapedSearchText = 
[searchText    stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSString *urlString = 
[NSString stringWithFormat:
@"http://services.faa.gov/airport/status/%@? format=application/json", escapedSearchText];
NSURL *url = [NSURL URLWithString:urlString];
return url;
}

- (NSString *)performAirportRequestWithURL:(NSURL *)url
{
NSError *error;
NSString *resultString = [NSString stringWithContentsOfURL:
url encoding:NSUTF8StringEncoding error:&error];
if (resultString == nil) {
    NSLog(@"Download Error: %@", error);
    return nil;
}
return resultString;
}

- (void)showNetworkError
{
UIAlertView *alertView = [[UIAlertView alloc]
                          initWithTitle:@"Whoops..."
                          message:@"There was an error reading 
                          from the FAA Server. Please      try again."
                          delegate:nil
                          cancelButtonTitle:@"OK"
                          otherButtonTitles:nil];
[alertView show];
}


- (NSDictionary *)parseJSON:(NSString *)jsonString
{
NSData *data = [jsonString dataUsingEncoding:NSUTF8StringEncoding];

NSError *error;
id resultObject = [NSJSONSerialization JSONObjectWithData:data options:
kNilOptions     error:&error];
if (resultObject == nil) {
    NSLog(@"JSON Error: %@", error);
    return nil;

    if (![resultObject isKindOfClass:[NSDictionary class]]) {
        NSLog(@"JSON Error: Expected dictionary");
        return nil;
    }
}
return resultObject;
}

@end`

Answer 1

Here is your issue: You are instantiating the airportDelays array every time a new dictionary is created, therefore, you are only adding one dictionary before destroying the airportDelay array and creating a new one. See below

self.airportDelays = [[NSMutableArray alloc] initWithCapacity:9];


[self parseDelay:dictionary];

Should be

if (!self.airportDelays) {
    self.airportDelays = [[NSMutableArray alloc] initWithCapacity:9];
}
[self parseDelay:dictionary];

I’m also weary of you using a for loop to do your network operations. You should probably be using a different queueing mechanism, where the program waits for the response for the first dictionary before asking the webservice for the next. That might be a different lesson for a different time though.

Good luck