如何在没有Interface Builder的情况下创建Cocoa接口？

let window = NSWindow(contentRect: NSMakeRect(0, 0, 800, 600), styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView], backing: .buffered, defer: false)

let contentView = NSView(frame: NSMakeRect(0, 0, 800, 600))
contentView.wantsLayer = true

let label = NSTextField(labelWithString: "Hello, world!")
label.frame = NSMakeRect(200, 200, 400, 40)
contentView.addSubview(label)

window.contentView = contentView
window.center()
window.makeKeyAndOrderFront(nil)

class AppDelegate: NSObject, NSApplicationDelegate {
    func applicationDidFinishLaunching(_ notification: Notification) {
        // Add code here to handle the event
    }
}