How to return a value from CLGeocoder? - ios

Question

I'm working on the weather app as a training and there's a need to convert location to city. So I'm using CLGeocoder like so:
func updateWeatherData(json: JSON?) {
if let json = json {
weatherData.temperature = fahrenheitToCelcius(json["currently"]["temperature"].doubleValue)
weatherData.weatherIconName = json["currently"]["icon"].stringValue
let location = CLLocation(latitude: json["latitude"].doubleValue, longitude: json["longitude"].doubleValue)
CLGeocoder().reverseGeocodeLocation(location) { (placemark, error) in
if let city = placemark {
self.weatherData.city = city.last?.locality
} else if let error = error {
print(error)
}
}
updateUIWithWeatherData()
}
}
//MARK: - UI Updates
func updateUIWithWeatherData() {
cityLabel.text = weatherData.city
temperatureLabel.text = "\(weatherData.temperature)°"
weatherIcon.image = UIImage(named: weatherData.weatherIconName!)
}
And this code returns nil to weatherData.city. But when I place a breakpoint inside a closure, everything works fine. What am I missing?

Answer 1

If I understand your issue correctly you need to update your UI after the geocoding is complete. Like the following:
func updateWeatherData(json: JSON?) {
if let json = json {
weatherData.temperature = fahrenheitToCelcius(json["currently"]["temperature"].doubleValue)
weatherData.weatherIconName = json["currently"]["icon"].stringValue
let location = CLLocation(latitude: json["latitude"].doubleValue, longitude: json["longitude"].doubleValue)
CLGeocoder().reverseGeocodeLocation(location) { (placemark, error) in
if let city = placemark {
self.weatherData.city = city.last?.locality
} else if let error = error {
print(error)
}
self.updateUIWithWeatherData()
}
}
}
The order of these operations is so that the geocoding is done asynchronously and may occur later then the code called after it. Note may but does not need to.
You should also read documentation of this method about threading. UI must be updated on main thread so unless the documentation specifies that the call will be done on main thread you are best forcing it:
CLGeocoder().reverseGeocodeLocation(location) { (placemark, error) in
if let city = placemark {
self.weatherData.city = city.last?.locality
} else if let error = error {
print(error)
}
DispatchQueue.main.async {
self.updateUIWithWeatherData()
}
}