アプリの初回起動の限定の処理について

アプリをインストールした直後に一回だけ NavigationBar のタイトルを決める処理をしたいのですが書いたコードが実行されない理由はなんですか？　又、どの様にしたら実行される様になりますか?

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    static let share = AppDelegate()

    var window: UIWindow?

    var theFarstNameDidSet : ((_ nowNumber : String) -> Void)? = nil
    var theFarstBool = false

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool { //ここが初回起動のコードらしい。

        // Override point for customization after application launch.
        print("最初に実行")
        self.theFarstBool = true
        self.theFarstNameDidSet?("")
        print("最後に実行")
        self.theFarstBool = false
        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {
        // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
        // Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game.
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
        // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
    }

    func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
    }


}

import UIKit


class ViewController: UIViewController {


    @IBOutlet weak var characterImage: UIImageView!
    @IBOutlet weak var timerlabel: UILabel!
    @IBOutlet weak var startButton: UIButton!

    let userDefaults = UserDefaults.standard
    let fastTitleKey = "fastTitleKey"

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        startButton.layer.cornerRadius = 25.0

        guard let obj = UserDefaults.standard.object(forKey: "goalCountKey") else {
            return
        }

        let goalString = "\(obj)"
        timerlabel.text = secondsToGoalTimerLabel(Int(goalString)!)

        if AppDelegate.share.theFarstBool == true {
            print("２番目に実行")
            AppDelegate.share.theFarstNameDidSet = { nowNumber in
                var alertTextFeld: UITextField?
                let alert = UIAlertController(title: "Skill Name", message: "Enter new name", preferredStyle: UIAlertController.Style.alert)
                alert.addTextField { (textField: UITextField!) in
                    alertTextFeld = textField
                }

                alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { _ in
                    if let text = alertTextFeld?.text {
                       self.title = text
                        self.userDefaults.set(text, forKey: self.fastTitleKey)
                        self.userDefaults.synchronize()

                    }
                }))
                self.present(alert, animated: true, completion: nil)
            }

        }


        self.title = self.userDefaults.object(forKey: self.fastTitleKey) as? String

     }

    override func viewWillAppear(_ animated: Bool) {

        guard let obj = UserDefaults.standard.object(forKey: "goalCountKey") else {
            return
        }

        let goalString = "\(obj)"
        timerlabel.text = secondsToGoalTimerLabel(Int(goalString)!)
    }

}