我正在尝试更改标签的文本或在我的 iOS 应用程序从后台状态变为活动状态时显示警报。
当我调用 ViewController 类中的函数时，只有 print() 方法可以正常工作。但是当我想与该类中的对象交互时，它会显示错误。
SceneDelegate.swift：
var vc = ViewController()
func sceneDidBecomeActive(_ scene: UIScene) {
// Called when the scene has moved from an inactive state to an active state.
// Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
vc.showMessage("Test message")
}
ViewController.swift：
@IBOutlet weak var textLabel: UILabel!
func showMessage(_ incomingMessage:String!) {
let warning = UIAlertController(title: "Warning", message: incomingMessage, preferredStyle: .alert)
let aButton = UIAlertAction(title: "OK", …