Connect a menu item

(Swift 5, macOS, Xcode 11, Storyboards)

I try to connect a menu button. I have googled it intensely and I am confused as there is little updated information. I am new and I am confused.

What I have tried is to control drag from the menu button to the AppDelegate.swift and I have created an action. It works well if I print something. But I do not understand how can I make do something to an NSView or a label. For instance, in this example, I put a blue NSView in the storyboard and I try to fadeOut when I click button1 on the Menu. (In iOS I would put an outlet in the viewController.swift. But in macOS I suppose, it should be in the AppDelegate.swift? If I try to control drag from the NSView to the AppDelegate, it is not possible)

I put that in the AppDelegate.swift:

@IBActionfunc button1(_ sender: NSMenuItem) {
     
        print ("I click to button1 in the menu")
   
        // When I add that, I have an error: use of unresolved identifier 'nsView1'. 
        // I do not know how to connect nsView1 with the button, if the button is in the AppDelegate.swift)
        NSAnimationContext.runAnimationGroup({ (context) in
          context.duration = 2.0
            nsView1.animator().alphaValue = 0
    }

    }

I put that in the ViewController.swift:

overridefunc viewDidLoad() {
        super.viewDidLoad()
      
        nsView1.wantsLayer = true
        nsView1.layer!.backgroundColor = NSColor.blue.cgColor

    }

Where I should I put that and how to make the button recognize the nsView1 ?:

@IBOutletweakvar nsView1: NSView!