Calling function from another Swift class

I'm having trouble calling a function in my GameViewController.swift from another class, Menu.swift. I call the function like this:

class Menu: SKnode {
    func scoreAction(sender:UIButton!) { 
        self.buttonPlay.removeFromSuperview()
        self.buttonScore.removeFromSuperview()
         // CALLING FUNCTION
        GameViewController.showLeaderboard()    
     }
}

And here is the function I'm trying to call:

class GameViewController: UIViewController, UITextFieldDelegate, GKGameCenterControllerDelegate  {
 
   func showLeaderboard() {
      var gcViewController: GKGameCenterViewController = GKGameCenterViewController()
      gcViewController.gameCenterDelegate = self
    
      gcViewController.viewState = GKGameCenterViewControllerState.Leaderboards
      gcViewController.leaderboardIdentifier = "yourleaderboardid"
    
      self.presentViewController(gcViewController, animated: true, completion: nil)
    }
}

I have a compiler error inside my Menu class in the line GameViewController.showLeaderboard()

Missing argument for parameter #1 in call

but I don't understand what type of argument the compiler is expecting because I declared the function without needing any parameters.

In GameViewController you have defined scoreAction as instance method not the class function.You should call scoreAction by making instance of GameViewController

class Menu: SKnode {

    func scoreAction(sender:UIButton!) { 
        self.buttonPlay.removeFromSuperview()
        self.buttonScore.removeFromSuperview()
         // CALLING FUNCTION 
         //see () on GameViewController
        GameViewController().showLeaderboard()    
     }
}

I think you should load GameViewController from storyBoard if you have GameViewController in storyBoard