没有Interface Builder的Cocoa,初始化app控制器的实例？

import Cocoa

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
    var window: NSWindow!

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        // 创建一个新的窗口
        let window = NSWindow(contentRect: NSMakeRect(0, 0, 480, 300),
                              styleMask: [.titled, .closable, .miniaturizable, .resizable],
                              backing: .buffered,
                              defer: false)
        window.center()
        window.title = "My App"
        window.makeKeyAndOrderFront(nil)
        self.window = window
    }

    func applicationWillTerminate(_ aNotification: Notification) {
        // 在这里执行任何需要在应用程序退出前完成的操作
    }
}