Swift 如何在调用“viewDidLoad”之前加载self.navigationController

我想在视图控制器调用viewDidLoad之前做一些事情。我调用了loadViewIfNeeded（）但self.navigationController仍然为零。我怎样才能加载它

AppDelegate.swift BindableType.swift 斯威夫特

---

我发现了问题。我必须在viewController.bind（到：viewModel）

func someMethod() {
    var viewController = Storyboard.instantiate()
    let viewModel = SomeViewModel()
    vc.bind(to: viewModel)
}

protocol BindableType {
    associatedtype ViewModelType

    var viewModel: ViewModelType! { get set }

    func bindViewModel()
}

extension BindableType where Self: UIViewController {
    mutating func bind(to model: Self.ViewModelType) {
        viewModel = model
        loadViewIfNeeded()

        // PROBLEM HERE: navigationController is nil, but view have been loaded
        navigationController?.navigationBar.prefersLargeTitles = true
        navigationController?.navigationItem.largeTitleDisplayMode = .automatic

        bindViewModel()
    }
}

class SomeViewController: BindableType {

    override func viewDidLoad() {
        super.viewDidLoad()

        // navigationController?.navigationBar.prefersLargeTitles = true
        // navigationController?.navigationItem.largeTitleDisplayMode = .automatic
    }

    func bindViewModel() {
        ...
    }
}

self.navigationViewController.pushViewController(viewController, animated: true)
viewController.bind(to: viewModel)