即使在賦值后，弱可選變數也顯示為零？

我有一個 LoginCoordinator 類，它的 start() 方法實體化了 LoginViewController。但即使在從 LoginCoordinator 分配 LoginViewController 中的 coordinator 變數之后，“有時”視圖控制器中的 coordinator 變數也為零。

“有時”我的意思是，當我除錯并在 start() 方法中保留斷點時，會分配該值。

這是我的登錄協調器

class LoginCoordinator: Coordinator {
var navigationController: UINavigationController
weak var parent: MainCoordinator?
var childCoordinators: [Coordinator]?


init(navController: UINavigationController) {
    self.navigationController = navController
}

func start() {
    let vc: LoginViewController = UIStoryboard.main.instantiateViewController()
    vc.coordinator = self
    navigationController.pushViewController(vc,animated: true)
}

func goToSignUp() {
    let signUpCoordinator = SignUpCoordinator(navController: navigationController)
    childCoordinators?.append(signUpCoordinator)
    signUpCoordinator.start()
}

func goToHomeVC() {
    let homeCoordinator = HomeCoordinator(navControl: navigationController)
    childCoordinators?.append(homeCoordinator)
    homeCoordinator.start()
 }
}

這是我的 LoginViewController

class LoginViewController: UIViewController {

@IBOutlet weak private var userName: HubTextField!
@IBOutlet weak private var password: HubTextField!
@IBOutlet weak private var forgotPassword: UILabel!
@IBOutlet weak var loginButton: HubButton!
var viewModel: LoginSignupVM = .init(totalItem: 2)
weak var coordinator: LoginCoordinator?

fileprivate func setupForgotPassword() {
    forgotPassword.isUserInteractionEnabled = true
    let tapGesture = UITapGestureRecognizer(target: self, action: #selector(forgotTapped))
    forgotPassword.addGestureRecognizer(tapGesture)
}

override func viewDidLoad() {
    super.viewDidLoad()
    loginButton.appearance = Appearance(cornerRadius: loginButton.frame.height/2)
    loginButton.setTitle(TitleText.loginText, for: .normal)
    loginButton.isEnabled = false
    setupTextField()
    hideKeyboardWhenTappedAround()
    setupForgotPassword()
    setupNavigationBar()
    
    // MARK: remove this later
    userName.text = "[email protected]"
    password.text = "asdfg123"
}

private func setupNavigationBar() {
    let titleView = UILabel(frame: .zero)
    titleView.text = "Login Up"
    titleView.font = UIFont.systemFont(ofSize: 20)
    navigationItem.titleView = titleView
    rightButton()
}

fileprivate func rightButton() {
    let rightButton = UIBarButtonItem(title: "signUp", style: .plain, target: self, action: #selector(goToSignUPScreen))
    rightButton.title = "sign Up"
    navigationItem.rightBarButtonItem = rightButton
}

@objc private func goToSignUPScreen() {
    coordinator?.goToSignUp()
}

@objc private func backButtonClicked() {
    navigationController?.popViewController(animated: true)
}

@objc private func forgotTapped() {
    //MARK: todo forgot password
}

private func assignTags() {
    userName.tag = 0
    password.tag = 1
}

private func setupTextField() {
    userName.placeHolder = TitleText.email
    userName.textFieldType = .email
    userName.delegate = self
    password.placeHolder = TitleText.password
    password.textFieldType = .password
    password.delegate = self
    assignTags()
}

private func goToHomeViewController() {
    coordinator?.goToHomeVC()
}

@IBAction func onLoginClick(_ sender: Any) {
    //MARK: todo login click change hardcoded verification
    if let email = userName.text, let password = password.text {
        if email == "[email protected]" && password == "asdfg123" {
            goToHomeViewController()
        }
    }
  }
}

extension LoginViewController: ValidatorButton {
func addNewValidated(tag: Int, result: ValidationResult) {
    viewModel.validationList[tag] = result
    loginButton.isEnabled = viewModel.loginButtonEnabled()
   }
  }

從 MainCoordinator 呼叫 LoginCoordinator 為：

class MainCoordinator: Coordinator {
var isLogin: Bool = false
var navigationController: UINavigationController
var childCoordinators: [Coordinator]? = []
let window: UIWindow?

init(navController: UINavigationController, window: UIWindow) {
    self.navigationController = navController
    self.window = window
}

func start() {
    if isLogin {
       let child = HomeCoordinator(navControl: navigationController)
        childCoordinators?.append(child)
        child.start()
    } else {
    let child = LoginCoordinator(navController: 
navigationController)
        childCoordinators?.append(child)
        child.start()
    }
   } 
}

并且 MainCoordinator 是從 sceneDelegate 呼叫的，如下所示：

   func scene(_ scene: UIScene, willConnectTo session: 
UISceneSession, options connectionOptions: 
UIScene.ConnectionOptions) {
    guard let scene = (scene as? UIWindowScene) else { return }
    let window = UIWindow(windowScene: scene)
    self.window = window
    
    let navigationController = UINavigationController()
    let mainCoordinator = MainCoordinator(navController: 
  navigationController,window: window)
    mainCoordinator.start()
    window.rootViewController = navigationController
    window.makeKeyAndVisible()
  }

uj5u.com熱心網友回復：

mainCoordinator在willConnectTo委托方法中被宣告為區域變數：

let mainCoordinator = MainCoordinator(navController: 
    navigationController,window: window)

這意味著它可以在willConnectTo.

由于mainCoordinator持有對 的唯一強參考LoginCoordinator，它也將被釋放。這就是為什么您nil在視圖控制器中看到的原因- 那時，mainCoordinator已被釋放。

你仍然會在 中看到一個非 nil 值LoginCoordinator.start，因為那時mainCoordinator.start還沒有完成，所以mainCoordinator還沒有被釋放。

為了解決這個問題，您可以通過宣告一個名為 的屬性，使場景委托持有對主協調器的強參考mainCoordinator：

var mainCoordinator: MainCoordinator!

// in willConnectTo:
mainCoordinator = MainCoordinator(navController: 
    navigationController,window: window)

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