swift中具有模式窗口的NSToolbar

import Cocoa

class ViewController: NSViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Create a toolbar
        let toolbar = NSToolbar(identifier: NSToolbar.Identifier("MyToolbar"))
        toolbar.delegate = self
        
        // Set the toolbar for the window
        if let window = view.window {
            window.toolbar = toolbar
        }
    }
    
    // Show the modal window
    @IBAction func showModalWindow(_ sender: Any) {
        let modalViewController = ModalViewController()
        
        if let window = view.window {
            window.beginSheet(modalViewController.view.window!, completionHandler: nil)
        }
    }
}

extension ViewController: NSToolbarDelegate {
    
    func toolbarAllowedItemIdentifiers(_ toolbar: NSToolbar) -> [NSToolbarItem.Identifier] {
        return [.showModal]
    }
    
    func toolbarDefaultItemIdentifiers(_ toolbar: NSToolbar) -> [NSToolbarItem.Identifier] {
        return [.showModal]
    }
    
    func toolbar(_ toolbar: NSToolbar, itemForItemIdentifier itemIdentifier: NSToolbarItem.Identifier, willBeInsertedIntoToolbar flag: Bool) -> NSToolbarItem? {
        let toolbarItem = NSToolbarItem(itemIdentifier: itemIdentifier)
        
        switch itemIdentifier {
        case .showModal:
            toolbarItem.label = "Show Modal"
            toolbarItem.target = self
            toolbarItem.action = #selector(showModalWindow(_:))
            toolbarItem.image = NSImage(named: NSImage.Name("modal_icon"))
        default:
            break
        }
        
        return toolbarItem
    }
}

class ModalViewController: NSViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Set up the content view for the modal window
        let contentView = NSView(frame: NSRect(x: 0, y: 0, width: 300, height: 200))
        contentView.wantsLayer = true
        contentView.layer?.backgroundColor = NSColor.white.cgColor
        
        view = contentView
    }
}