Core Location returning 00 - iphone

Question

Here's the full method, I didn't put the second half originally because I know it works:
-(void)showDirections
{
locationManager = [[CLLocationManager alloc] init];
[locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters];
[locationManager setDelegate:self];
CLLocation *location = [locationManager location];
CLLocationCoordinate2D coordinate = [location coordinate];
NSNumber *myLatitude = [NSNumber numberWithDouble:coordinate.latitude];
NSNumber *myLongitude = [NSNumber numberWithDouble:coordinate.longitude];
double myLatitude2 = [myLatitude doubleValue];
double myLongitude2 = [myLongitude doubleValue];
NSArray *array = [dataHold objectForKey:#"Subtree"];
NSString *latitude = [NSString stringWithFormat:#"%#",[array objectAtIndex:4]];
NSString *longitude = [NSString stringWithFormat:#"%#",[array objectAtIndex:5]];
double clubLatitude = [latitude doubleValue];
double clubLongitude = [longitude doubleValue];
CLLocationCoordinate2D start = { myLatitude2, myLongitude2};
CLLocationCoordinate2D destination = { clubLatitude, clubLongitude};
NSString *googleMapsURLString = [NSString stringWithFormat:#"http://maps.google.com/?saddr=%1.6f,%1.6f&daddr=%1.6f,%1.6f",start.latitude, start.longitude, destination.latitude, destination.longitude];
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:googleMapsURLString]];
}

Answer 1

Two issues:
1) You are doing a NSNumber box/unbox cycle that has no use whatsoever
2) Core Location is asynchronous, therefore you cannot return the user's location straight away, you must use the delegate method(s) to retrieve the location if/when it is available.
Here's an example of how it should work:
-(void)showDirections
{
locationManager = [[CLLocationManager alloc] init];
[locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters];
[locationManager setDelegate:self];
[locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
CLLocationCoordinate2D coord = [newLocation coordinate];
NSArray *array = [dataHold objectForKey:#"Subtree"];
NSString *latitude = [NSString stringWithFormat:#"%#",[array objectAtIndex:4]];
NSString *longitude = [NSString stringWithFormat:#"%#",[array objectAtIndex:5]];
double clubLatitude = [latitude doubleValue];
double clubLongitude = [longitude doubleValue];
NSString *googleMapsURLString = [NSString stringWithFormat:#"http://maps.google.com/?saddr=%1.6f,%1.6f&daddr=%1.6f,%1.6f", coord.latitude, coord.longitude, clubLatitude, clubLongitude];
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:googleMapsURLString]];
}

Answer 2

The fourth line of your code is where the problem begins. You cannot get the location instantly, you will need to wait until the location services notify the delegate that a location is available. I will add some comments to your code to explain:
-(void)showDirections
{
locationManager = [[CLLocationManager alloc] init];
[locationManager setDesiredAccuracy:kCLLocationAccuracyNearestTenMeters];
[locationManager setDelegate:self];
// this is not where you should be looking
CLLocation *location = [locationManager location];
// the rest of this function is not included in this example ...
}
Since you set the delegate as "self", the current class but implement the "CLLocationManagerDelegate" protocol, which defines the following two functions:
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { /* */ }
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error { /* */ }
That is where you will get a location provided to you.
Dont forget to update your class definition like so:
#interface MyClass : NSObject <CLLocationManagerDelegate> {
And as a side note, it seems like you do not fully understand delegates and the purpose that they serve, which is fine if you are new to Objective-C, but getting more familiar with them will certainly make your life a bit easier.
Some other helpful stuff:
A CoreLocation Tutorial (covers what you are trying to do)