swift - 我如何在最新的 swift 中编写 NSAlert？

Question

我正在尝试编写此警报:

func alertUser() {
        let alert = NSAlert()
        alert.messageText = "message 1"
        alert.informativeText = "info1"
        alert.informativeText = "info2"
        alert.addButton(withTitle: "NO")
        alert.addButton(withTitle: "YES")
        alert.beginSheetModal(for: self.view.window!) { (returnCode: NSModalResponse) -> Void in
            print ("returnCode: ", returnCode)
        }

但我在alert.beginSheetModal

行收到可怕的 unexpectedly found nil while unwrapping an Optional value消息

请告诉我我做错了什么。

谢谢

Answer 1

您应该从 viewDidAppear 运行您的代码，因为您的 View Controller 尚未在 viewDidLoad 中创建窗口对象。

override func viewDidAppear() {
    super.viewDidAppear()

    alertUser()
}