medium_checkAppVersion_01.swift

import UIKit
import SwiftyJSON

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        self.checkAppVersion()

        return true
    }

    func checkAppVersion() {
        let link = "https://itunes.apple.com/lookup?bundleId=com.###.YourBundleID"
        let url: URL = URL(string: link)!
        let session = URLSession.shared

        let request = NSMutableURLRequest(url: url)
        request.httpMethod = Constants.HttpMethod.get
        request.cachePolicy = URLRequest.CachePolicy.reloadIgnoringCacheData

        let task = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) in

            guard let data: Data = data, let _: URLResponse = response, error == nil else {
                print("ERROR at AppDelegate(checkAppVersion): Fetch App Info fail)")
                return
            }

            self.extractJSON(from: data)
        })

        task.resume()
    }

    func extractJSON(from data: Data) {
        do {
            let json = try JSON(data: data)
            print(json)
        } catch {
            print("ERROR at AppDelegate(extractJSON): \(error)")
            return
        }
    }
}