AppDelegate.swift崩溃macOS App

Question

当我尝试启动我的应用时，它只会崩溃。它给出的错误是unrecognized selector sent to instance 0x608000000ac0，错误显示在第4行的AppDelegate.swift文件中。这是完整的AppDelegate.swift文件：

import Cocoa

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate { //This is where I get the error

    @IBOutlet weak var window: NSWindow!

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        // Insert code here to initialize your application
    }

    func applicationWillTerminate(_ aNotification: Notification) {
        // Insert code here to tear down your application
    }

    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
        return true
    }
}

如何修复此错误？提前致谢， Aaronjam