iOS ต้องการ Check ตรวจสอบว่า iPhone มีการเปิด Enable บริการ GPS แล้วหรือยังเพื่อใช้บริการด้านสถานที่

- (void)locationManager: (CLLocationManager *)manager
       didFailWithError: (NSError *)error {

    NSString *errorString;
    [manager stopUpdatingLocation];
    NSLog(@"Error: %@",[error localizedDescription]);
    switch([error code]) {
        case kCLErrorDenied:
            //Access denied by user
            errorString = @"Access to Location Services denied by user";
            //Do something...
            break;
        case kCLErrorLocationUnknown:
            //Probably temporary...
            errorString = @"Location data unavailable";
            //Do something else...
            break;
        default:
            errorString = @"An unknown error has occurred";
            break;
        }
    }

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:errorString delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
    [alert show];
    [alert release];
}

if([CLLocationManager locationServicesEnabled])
      {
            NSLog(@"Enable GPS Complete");
      }
    else{
         UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error getting Current Location" message:@"Please check your Location Service!!" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alertView show];
        [alertView release];
        
      }