Calling function from another Swift class

Question

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.

You are trying to call showLeaderboard like a class method, but it is an instance method. You need to instantiate an instance of GameViewController and then you can call showLeaderboard. — Mobile Ben
– Mobile Ben, Commented Sep 28, 2014 at 5:55

Roland Keesom · Accepted Answer · 2015-03-19 09:01:38Z

69

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

edited Mar 19, 2015 at 9:01

Roland Keesom

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answered Sep 28, 2014 at 5:59

codester

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1 Comment

HangarRash Dec 20, 2024 at 0:31

Why does this have so many upvotes? This is wrong. You end up calling showLeaderboard() on a throwaway instance of GameViewController. Sure, it fixes the compiler error but at runtime, nothing is going to work as expected.

Dalija Prasnikar · Accepted Answer · 2024-12-19 21:11:51Z

12

If you want to perform any method on action in another class, you have to use protocol.

//Outside 1st class

protocol abc {
     func xyz()
}

//Inside 1st class

var delegate: abc?

//Inside 1st class on action

self.delegate.xyz()

//Inside 2nd class you want to perform method

extension 2nd: abc {
    func xyz(){
      //code 
   }
}

//Inside 2nd class where the instantiate process is performed

let obj = 2nd() //2nd initialiser
obj.delegate = self

// if you want to use this scenario with table view cell in cellForRowAt
guard let cell = tableView.dequeueReusableCell(withIdentifier: "TableViewCell", for: indexPath) as? TableViewCell else { return UITableViewCell() }
cell.delegate = self

Hope this helps.

edited Dec 19, 2024 at 21:11

Dalija Prasnikar♦

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answered Feb 24, 2018 at 9:32

Pratyush Pratik Sinha

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2 Comments

ClassA Over a year ago

Can you please explain what 2nd initialiser inside let obj = 2nd initialiser is?

Pratyush Pratik Sinha Over a year ago

let obj = 2nd initialiser Here obj is the object of 2nd initialiser like:- let cell = ?*(tableView.dequeueReusableCell(withIdentifier: "TVCSelectProfessionalForConsultation") as? TVCSelectProfessionalForConsultation) @ClassA

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