I have been banging my head in order to figure out how to fix this piece of code. Basically I have a piece of code that takes a string cityName and stores the latitude and longitude of it in a global variable and call it in another function right after. Apparently because of asynchronous call, I am not able to do that and the value of longitude and latitude are nil.

```
func findCityCoordinates(cityName: String)  {
        var geocoder = CLGeocoder()

        geocoder.geocodeAddressString(cityName, completionHandler: {(placemarks: [AnyObject]!, error: NSError!) -> Void in
            if let placemark = placemarks?[0] as? CLPlacemark {

              self.cityLatitude = placemark.location.coordinate.latitude //Returns nil
              self.cityLongitude = placemark.location.coordinate.longitude //Returns nil
            }
        })
    }

```

I have also been trying to work around completion handler but I have no idea on how to implement it and call it in a function. I would appreciate some help.