title: How to change UIButton image after clicking in Swift?
body: <p>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.</p>
  
  <pre><code>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 &gt; 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)
          }
      }
  }
  </code></pre>