ios - How to change UIButton image after clicking in Swift?

Question

I'm new to coding development so this should be a pretty noob question. But I'm trying to change the image of my UIButton to an image stored in image.casset "duellogo" if my if statement executes. But I am unsure how to change UIButton Image; I only know how to change UIImageView Image.

import UIKit

class ViewController: UIViewController 
{

    @IBOutlet weak var firstCardImageView: UIImageView!
    @IBOutlet weak var secondCardImageView: UIImageView!
    @IBOutlet weak var playRoundButton: UIButton!
    @IBOutlet weak var backgroundImageView: UIImageView!

    @IBOutlet weak var Player1Score: UILabel!
    @IBOutlet weak var Player2Score: UILabel!

    //declaring index score, 0, to player 1 and player 2
    var player1Total=0
    var player2Total=0

    var cardNamesArray:[String] = ["ace", "card2", "card3", "card4", "card5", "card6", "card7", "card8", "card9", "card10", "jack", "queen", "king"]

    override func viewDidLoad() 
    {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() 
    {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func playRoundTapped(sender: UIButton) 
    {
        // create variable to make a random number from 1-13
        var firstRandomNumber:Int = Int(arc4random_uniform(13))
        var firstCardString:String = self.cardNamesArray[firstRandomNumber]
        self.firstCardImageView.image = UIImage(named: firstCardString)

        // create variable to make a random number from 1-13 for second card
        var secondRandomNumber = Int(arc4random_uniform(13))
        var secondCardString:String = self.cardNamesArray[secondRandomNumber]
        self.secondCardImageView.image = UIImage(named: secondCardString)


        // Determine the higher card
        if firstRandomNumber > secondRandomNumber{
            //TODO: first card is lager
            player1Total+=1
            self.Player1Score.text = String(player1Total)
        }else if(firstRandomNumber == secondRandomNumber){
            // ERROR: TRYING TO CHANGE BUTTON IMAGE
            self.playRoundButton.setImage("duellogo", forState: UIControlState.Normal)
            //    ^^ ERROR
        }else{
            //TODO: second card is larger
            player2Total+=1
            self.Player2Score.text = String(player2Total)
        }
    }
}

Answer 1

Try this code

let image = UIImage(named: "duellogo.png") as UIImage!
self.playRoundButton.setImage(image, forState: .Normal)