Where is the correct place to build the needed Window for app in Cocoa macOS - swift

Question

I am confused to find the concert way for building the needed Window for app, so one of source say that I have to use this down code:
import Cocoa
import SwiftUI
class ViewController: NSViewController {
override func viewWillAppear() {
self.view = NSHostingView(rootView: ContentView())
self.view.window?.makeKeyAndOrderFront(nil)
self.view.window?.standardWindowButton(NSWindow.ButtonType.zoomButton)?.isHidden = true
self.view.window?.standardWindowButton(NSWindow.ButtonType.miniaturizeButton)?.isHidden = true
self.view.window?.standardWindowButton(NSWindow.ButtonType.closeButton)?.isHidden = true
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override var representedObject: Any? {
didSet {
// Update the view, if already loaded.
}
}
}
And some other source says I have use this code:
#main
class AppDelegate: NSObject, NSApplicationDelegate {
func applicationDidFinishLaunching(_ aNotification: Notification) {
// Insert code here to initialize your application
let window = NSWindow(
contentRect: NSRect(x: 0, y: 0, width: 300, height: 300),
styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
backing: .buffered, defer: false)
window.center()
window.setFrameAutosaveName("Main Window")
window.contentView = NSHostingView(rootView: ContentView())
window.makeKeyAndOrderFront(nil)
window.standardWindowButton(NSWindow.ButtonType.zoomButton)?.isHidden = true
window.standardWindowButton(NSWindow.ButtonType.miniaturizeButton)?.isHidden = true
window.standardWindowButton(NSWindow.ButtonType.closeButton)?.isHidden = true
}
func applicationWillTerminate(_ aNotification: Notification) {
// Insert code here to tear down your application
}
func applicationSupportsSecureRestorableState(_ app: NSApplication) -> Bool {
return true
}
}
Which I am really confused which one is needed and why? can some one explain it to me?