MainViewController.swift

class MainViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        checkForUpdate()
    }
    
    private func checkForUpdate() {
        ForceUpdateManager.shared.callback = { [unowned self] (appStoreUrl, isRequiredUpdate) -> Void in
            DispatchQueue.main.async {
                self.showUpdateAlert(appStoreUrl: appStoreUrl, isRequiredUpdate: isRequiredUpdate)
            }
        }
    }
    
    private func showUpdateAlert(appStoreUrl: String, isRequiredUpdate: Bool) {
        let title = isRequiredUpdate ? "Required App Update"
                                     : "New Update"
        
        let message = isRequiredUpdate ? "This update contains critical bug fixes, you need to update the app to continue browsing"  : "Please, update app to new version!"
        
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        
        alertController.addAction(UIAlertAction(title: "Update", style: .default, handler: { (_) in
            if let url = URL(string: appStoreUrl) {
                UIApplication.shared.open(url)
            }
        }))
        
        if !isRequiredUpdate {
            alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: { (_) in }))
        }
        
        present(alertController, animated: true)
    }
}