Cannot AddObject to NSMutableArray from Block

Question

I have a feeling that my problem here is really with blocking, but maybe it\'s something else too. I am trying to forward geocode an address and place the coordinates into an ar

Answer 1

if geocodeAddressString is async operation than your block will be performed after

NSLog(@"Array: %@", coordinates[0]);

also, after call of your method ends (when event already handled) the coordinates array released (it is because of __block modifier - blocks do not retain objects with __block modifier), and in your block you try to use dealloced coordinates array.

Once again:

Your block will be called after NSLog(@"Array: %@", coordinates[0]);

f.e.:

1. Remove NSLog(@"Array: %@", coordinates[0]); - it is normal that in that moment array is empty.
2. Store your coordinates array in some @property , you can release it after using in block

UPDATE:

in .h file

typedef void (^ConverteArrayCallback)(NSArray *coordinates); 

under @intrerface

- (void)convertAddressToGeocode:(NSString *)addressString callback:(ConverteArrayCallback) callback;

in .m file

- (void)convertAddressToGeocode:(NSString *)addressString callback:(ConverteArrayCallback) callback { 
    NSMutableArray *coordinates = [[NSMutableArray alloc] initWithCapacity:0];
    CLGeocoder *geocoder = [[CLGeocoder alloc] init];

    [geocoder geocodeAddressString:addressString
             completionHandler:^ (NSArray* placemarks, NSError* error) {
                 for (CLPlacemark* aPlacemark in placemarks)
                 {
                     // Process the placemark.
                     if (error){
                         NSLog(@"Geocode failed with error: %@", error);
                         [self displayError:error];
                         return;
                     }
                     else {

                         NSArray const *keys = @[@"coordinate.latitude",
                                                 @"coordinate.longitude",
                                                 @"altitude",
                                                 @"horizontalAccuracy",
                                                 @"verticalAccuracy",
                                                 @"course",
                                                 @"speed",
                                                 @"timestamp"];

                         NSString *keylat = keys[0];
                         NSString *keylng = keys[1];

                         if (aPlacemark.location == nil)
                         {
                             NSLog(@"location is nil.");

                         }
                         else if ([keylat isEqualToString:@"coordinate.latitude"] && [keylng isEqualToString:@"coordinate.longitude"])
                         {
                             NSString *lat = @"";
                             NSString *lng = @"";
                             lat = [self displayStringForDouble: [aPlacemark.location coordinate].latitude];
                             lng = [self displayStringForDouble: [aPlacemark.location coordinate].longitude];

                                 NSLog(@"This never gets executed"): //THIS NEVER GETS EXECUTED
                                 [coordinates addObject:[NSString stringWithFormat:@"%@",lat]];
                                 [coordinates addObject:[NSString s

tringWithFormat:@"%@",lng]];
                                 }}}

                           if (callback != NULL) {
                                 callback(coordinates);
                           }

      }];
}

That should works!

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    NSString *addressToSearch = self.addressSearchField.text;
    [self convertAddressToGeocode:addressToSearch callback:^(NSArray *coordinates)
      {  
       self.textView.text = [coordinates objectAtIndex:0];
      }];
}

Answer 2

__block NSMutableArray *coordinates = [[NSMutableArray alloc] initWithCapacity:0];

The problem is here; just replace the above code with:

NSMutableArray *coordinates = [[NSMutableArray alloc] init];