Having trouble using lazy with a var in swift - ios

Question

I am following the standford ios class for Fall 2017. As the professor goes through the demo, I follow by inputting and running like he does. He shows how using lazy with a var allows one to use the UIButton count for variable initialization. When I add the lazy keyword, the error doesn't go away. Thinking it was maybe an xcode update related problem, I downloaded someone else's version of the project and that project doesn't have the issue. The code is below, any thoughts? :/
class ViewController: UIViewController {
lazy var game = ConcentrationModel(numberOfPairsOfCards: (cardButtons.count + 1) / 2)
//Could have had var flipCount: Int = 0
//But it is inferred
var flipCount = 0 {
didSet {
flipCountLabel.text = "Flips: \(flipCount)"
}
}
var emojiChoices = ["🎃","👻","👿","🎃","👻","👿"]
#IBOutlet var cardButtons: [UIButton]!
#IBOutlet weak var flipCountLabel: UILabel!
#IBAction func touchCard(_ sender: UIButton) {
flipCount += 1
if let cardNumber = cardButtons.index(of: sender) {
flipCard(withEmoji: emojiChoices[cardNumber], on: sender)
print("cardNumber = \(cardNumber)")
} else {
print("chosen card was not in cardButtons")
}
print("agh!!! a ghost")
}
func flipCard(withEmoji emoji: String, on button: UIButton) {
if button.currentTitle == emoji {
button.setTitle("", for: UIControlState.normal)
button.backgroundColor = #colorLiteral(red: 1, green: 0.5763723254, blue: 0, alpha: 1)
} else {
button.setTitle(emoji, for: UIControlState.normal)
button.backgroundColor = #colorLiteral(red: 0.9999960065, green: 1, blue: 1, alpha: 1)
}
}
}

Answer 1

To initialize a lazy property which depends on the value of another property you have to use the closure syntax
lazy var game : ConcentrationModel = {
return ConcentrationModel(numberOfPairsOfCards: (self.cardButtons.count + 1) / 2)
}()