GPS 좌표로 도시 이름 알아내기

• 오프라인에서 할려면?

• 왜냐? 네트웍 안쓰고 하려니까...

• https://github.com/thampiman/reverse-geocoder/tree/master/reverse_geocoder (csv가 부족)

• https://github.com/daveross/offline-country-reverse-geocoder

• https://github.com/turgos/Location

• http://download.geonames.org/export/dump/ (자료)

• 미리 만들어진 테이블을 이용해서 가장 가까운 gps 좌표를 찾는 방식

• 실패할때만 online geocoder 를 사용하는 식으로 처리 하는 것도 좋을 듯

online geocoder - CLLocation 은 네트웍을 사용한다.

• https://developer.apple.com/documentation/corelocation/clgeocoder
• https://developer.apple.com/documentation/corelocation/converting_between_coordinates_and_user-friendly_place_names

To use a geocoder object, you create it and call one of its forward- or reverse-geocoding methods to begin the request. Reverse-geocoding requests take a latitude and longitude value and find a user-readable address. Forward-geocoding requests take a user-readable address and find the corresponding latitude and longitude value.

주소 -> gps 좌표 (geocoder)

import CoreLocation

var geocoder = CLGeocoder()
geocoder.geocodeAddressString("your address") {
    placemarks, error in
    let placemark = placemarks?.first
    let lat = placemark?.location?.coordinate.latitude
    let lon = placemark?.location?.coordinate.longitude
    print("Lat: \(lat), Lon: \(lon)")
}

gps 좌표 -> 주소 (reverse geocoder)

func lookUpCurrentLocation(completionHandler: @escaping (CLPlacemark?)
                -> Void ) {
    // Use the last reported location.
    if let lastLocation = self.locationManager.location {
        let geocoder = CLGeocoder()
            
        // Look up the location and pass it to the completion handler
        geocoder.reverseGeocodeLocation(lastLocation, 
                    completionHandler: { (placemarks, error) in
            if error == nil {
                let firstLocation = placemarks?[0]
                completionHandler(firstLocation)
            }
            else {
	         // An error occurred during geocoding.
                completionHandler(nil)
            }
        })
    }
    else {
        // No location was available.
        completionHandler(nil)
    }
}

// https://cocoacasts.com/reverse-geocoding-with-clgeocoder