swift - 展开时 window.rootViewController nil

Question

我想通过使用文件在我的 Swift 项目中使用 Coordinator Navigator()，但我需要将UINavigationController内部传递给navigator.show().

问题是 XCode 显示此错误：

Fatal Error: Unexpectedly found nil while unwrapping an Optional value in window!

应用委托

class AppDelegate: UIResponder, UIApplicationDelegate {

  var window: UIWindow!
  let navigator = Navigator()

  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

    let feedNavigation = window!.rootViewController!  as! UINavigationController
    navigator.show(segue: .listBeer, sender: feedNavigation)
    
    return true
  }
}

如何将其window.rootViewController! as! UINavigationController 作为非可选值传递？