System.swift

class System {
    func openAppSetting() {
        if let bundleId = Bundle.main.bundleIdentifier,
           let settingUrl = URL(string: UIApplication.openSettingsURLString + bundleId),
           UIApplication.shared.canOpenURL(settingUrl) {
            UIApplication.shared.open(settingUrl, options: [:]) { _ in }
        }
    }

    func isSystemPushAllowed(completion: @escaping (Bool) -> Void) {
        UNUserNotificationCenter.current().getNotificationSettings { settings in
            if settings.authorizationStatus == .notDetermined || settings.authorizationStatus == .denied {
                completion(false)
            } else {
                completion(true)
            }
        }
    }

    func currentApplicationVersion() -> String {
        if let info = Bundle.main.infoDictionary,
           let currentVersion = info["CFBundleShortVersionString"] as? String {
            return currentVersion
        }
        return ""
    }

    func currentApplicationBuildNumber() -> String {
        if let info = Bundle.main.infoDictionary,
           let currentVersion = info["CFBundleVersion"] as? String {
            return currentVersion
        }
        return ""
    }

    func appStoreLatestVersion() -> Observable<String> {
        return Observable.create { emitter in
            let url = URL(string: "https://itunes.apple.com/lookup?id=\(APP_ID)")!
            let task = URLSession.shared.dataTask(with: URLRequest(url: url, cachePolicy: URLRequest.CachePolicy.reloadIgnoringLocalCacheData)) { data, _, error in
                guard error == nil, let data = data else {
                    emitter.onNext("")
                    return
                }

                guard let json = try? JSON(data: data),
                      let results = json["results"].array,
                      results.count > 0,
                      let version = results[0]["version"].string else {
                    emitter.onNext("")
                    return
                }

                emitter.onNext(version)
            }
            task.resume()

            return Disposables.create {
                task.cancel()
            }
        }.take(1)
    }
}