Passing CLGeocoder city name to new class UILabel - objective-c

Question

I´m currently trying to pass the city name retrieved by CLGeocoder successfully to a UILabel of another class. First the CLGecoder-class
FindLocation.h
#property (nonatomic, strong) NSString *cityName;
FindLocation.m - inside method (void)locationManager:(CLLocationManager *)manager...
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
if (self.isFirstUpdate) {
self.isFirstUpdate = NO;
return;
}
CLLocation *location = [locations lastObject];
if (location.horizontalAccuracy > 0) {
self.currentLocation = location;}
CLGeocoder *fgeo = [[CLGeocoder alloc] init];
// Reverse Geocode a CLLocation to a CLPlacemark
[fgeo reverseGeocodeLocation:location completionHandler:^(NSArray *placemarks, NSError
*error){
NSLog(#"%#", location);
// Make sure the geocoder did not produce an error
// before continuing
if(!error){
// Iterate through all of the placemarks returned
// and output them to the console
for(CLPlacemark *placemark in placemarks){
NSLog(#"%#",[placemark description]);
self.cityName = [placemark locality];
NSLog(#"city is %#",cityName); }
[self.locationManager stopUpdatingLocation];
[self.delegate findLocationDidGeocodeCityName:self.cityName];
} else {
// Our geocoder had an error, output a message
// to the console
NSLog(#"There was a reverse geocoding error\n%#",
[error localizedDescription]);
Further in my FirstViewController it looks like this:
FindLocation *cityname = [[FindLocation alloc] init];
[cityname cityName];
[self.cityLabel setText:(cityname.cityName)];
NSLog(#"CityName is...%#", cityname.cityName); //Log shows CityName is...(null)
I don´t know whats wrong here. Since the city is found there must be something wrong with the latter part of code, but I don´t know what. Is the passing of NSString - cityName implemented wrong?

Answer 1

I think the problem is that the geocode process is not instantaneous. You are instantiating FindLocation and then immediately trying to access cityName. However, even assuming that your init method triggers the location update, the geocoder will take a little bit of time to go to the server and get a response. Additionally, the location manager won't return a location immediately, and since it looks like that is what kicks off the geocoder, you have to wait a little bit longer for that as well.
One solution here would be to implement a delegate protocol on FindLocation so that it can notify FirstViewController when the geocoding has completed. Something like this:
FindLocation.h
#import <UIKit/UIKit.h>
#class FindLocation;
#protocol FindLocationDelegate <NSObject>
- (void)findLocationDidGeocodeCityName:(NSString *)cityName;
#end
#interface FindLocation : NSObject
#property (weak, nonatomic) id<FindLocationDelegate> delegate;
#end
and then in your CLGeocoder completionHandler after retrieving cityName:
[self.delegate findLocationDidGeocodeCityName:self.cityName];
Now, in FirstviewController.h, indicate that you conform to the FindLocationDelegate protocol:
#interface FirstViewController : UIViewController <FindLocationDelegate>
In your FirstViewController.m, set the delegate like so:
FindLocation *cityName = [[FindLocation alloc] init];
cityName.delegate = self;
and then also in FirstViewController, implement the delegate method:
#pragma mark - FindLocation Delegate
- (void)findLocationDidGeocodeCityName:(NSString *)cityName
{
[self.cityLabel setText:cityName];
}
There are other ways to do this as well, but the key is you have to wait until the completionHandler runs, and then notify any other interested objects about what got returned.