Distance Calculator

import UIKit
import CoreLocation

func distanceCalculator(preLat: Double?, preLng: Double?, postLat: Double?, postLng: Double?) -> String {
    guard let preLat = preLat, let preLng = preLng, let postLat = postLat, let postLng = postLng else {
        return ""
    }
    let preLocation = CLLocation(latitude: preLat, longitude: preLng)
    let postLocation = CLLocation(latitude: postLat, longitude: postLng)
    let distanceInMeters = preLocation.distance(from: postLocation)
    return String(distanceInMeters.rounded(.toNearestOrAwayFromZero))
}

let res = distanceCalculator(preLat: +37.33124551, preLng: -122.03073664, postLat: +37.33121136, postLng: -122.03073097)
print("RESULT is \(res)m")