Gmsgeocoder Reversegeocodecoordinate: Completionhandler: on Background Thread

GMSGeoCoder reverseGeocodeCoordinate: completionHandler: on background thread

Restructure your code to proceed after the async tasks are done:

This also has the benefit that you don't actively wait for stuff and block the main thread

e.g.:

- (void)checkCitiesWithCompletionBlock:(void (^)(BOOL same))
    //Checking user's city
    [[GMSGeocoder geocoder]reverseGeocodeCoordinate:self.locationManager.location.coordinate completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
        if (error) {
            NSLog(@"%@",[error description]);
        }
        id userCity=[[[response results] firstObject] locality];

        //Checking store's city
        [[GMSGeocoder geocoder]reverseGeocodeCoordinate:arounder.radiusCircularRegion.center completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
            if (error) {
                NSLog(@"%@",[error description]);
            }
            id arounderCity=[[[response results] firstObject] locality];

            same ([userCity isEqualToString:arounderCity]);
        }];
    }];
}   

Find the ios device current location using geolocation

Objective-C

CLLocation *location = [[CLLocation alloc]
                            initWithLatitude:+38.4112810
                            longitude:-122.8409780f];
CLGeocoder*myGeocoder = [[CLGeocoder alloc] init];

[myGeocoder
     reverseGeocodeLocation:location
     completionHandler:^(NSArray *placemarks, NSError *error) {

 if (error == nil && placemarks.count > 0){ 

      CLPlacemark *placemark = placemarks[0];

     NSLog(@"Country = %@", placemark.country); 

     NSLog(@"Postal Code = %@", placemark.postalCode);

     NSLog(@"Locality = %@", placemark.locality);
 }
 else if (error == nil && placemarks.count == 0){

     NSLog(@"No results were returned.");

  }
   else if (error != nil) {

      NSLog(@"An error occurred = %@", error);

    }
}];

Swift

func gecode(location:CLLocation)
{

    let geoCoder = CLGeocoder()

    geoCoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error) -> Void in

        if(error != nil)
        {
            return
        }

        if let placeMark = placemarks?[0] {

            if let country = placeMark.addressDictionary!["Country"] as? String {

                if country == "India" {

                    //
                }

            }

        }

    })

}

Comparing 2 cities from 2 locations in background

Do it like this:

-(BOOL)checkIfUserInRadiusForLocation:(SavedLocation*)location userCity: (NSString *) userCity locationCity: (NSString *) locationCity
{
    if(location.radiusString isEqualToString:@“1KM”)
    {
      if(location.circularRegion containsCoordinate:self.locationManager.location.coordinate)
      {
        return YES;
      }
    }else if(location.radiusString isEqualToString:@“5KM”)
    {
      if(location.circularRegion containsCoordinate:self.locationManager.location.coordinate)
      {
        return YES;
      }
    //Important part:
    }else if(location.radiusString isEqualToString:@“City”)
    {
      if([userCity isEqual: locationCity])
      {
        return YES;
      }
    }
return NO;
}

-(void)sendNotificationIfNeeded
{    
    if (self.muteEnabled==YES) { //Check if the user muted the app
        NSLog(@"Mute enabled");
        return;
    }
    SavedLocation* location = [self.savedLocations objectAtIndex:0];
    [[GMSGeocoder geocoder]reverseGeocodeCoordinate:self.locationManager.location.coordinate completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
    if (error) {
        NSLog(@"%@",[error description]);
    }
    NSString *userCity=[[[response results] firstObject] locality];
   [[GMSGeocoder geocoder]reverseGeocodeCoordinate:location.circularRegion.center completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
    if (error) {
        NSLog(@"%@",[error description]);
    }
    NSString *savedLocationCity=[[[response results] firstObject] locality];

    if([self checkIfUserInRadiusForLocation:location userCity: userCity locationCity: savedLocationCity])
    {
      UILocalNotification *notification=[self createNotification];
      [self sendNotification:notification];
    }
    }];
  }];
}

Why do we call completion on main thread in asynchronous function?

Yes, but it's often convenient to call completion handlers on the main queue, since it's common to want to update the UI, and calling UI updaters on the wrong queue is a common bug.

It is not required, nor even universally recommended, to make general-purpose async functions call back on the main queue. But for certain systems where the use cases are well-known, it's very convenient and helps prevent bugs.

The above example, of course, is not useful, and would be very unlikely to be found in production code. But that doesn't change the utility in specialized cases. Another common pattern is for the caller to pass a completion queue. That's also fine, particularly for very general-purpose tools (such as URLSession, which uses this approach).

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