inheritance - Swift - 从该类继承的 Cast 对象

Question

我收到此错误:无法将表达式的类型 '()' 转换为类型 $'T5'PlayingCard 继承自 Card，我知道 drawRandomCard 返回一个 PlayingCard。我怎样才能进行这种转换？

var deck = PlayingCardDeck()
var card = PlayingCard()

class ViewController: UIViewController {



override func viewDidLoad() {
    super.viewDidLoad()

}

@IBAction func cardTouchBtn(sender : UIButton) {

    if !sender.currentTitle{sender.setTitle("", forState: UIControlState.Normal)}
    if  sender.currentTitle.isEmpty{
        card = PlayingCard(deck.drawRandomCard())
        sender.setBackgroundImage(UIImage(named : "cardFront"), forState: UIControlState.Normal)
        sender.setTitle(card.contents, forState: UIControlState.Normal)
    }else{
        sender.setBackgroundImage(UIImage(named : "cardBack"), forState: UIControlState.Normal)
        sender.setTitle("", forState: UIControlState.Normal)
    }
}

}

git 上的完整代码:https://github.com/victoryudi/CS193p-Swift/tree/master/FlipCard

Answer 1

PlayingCard(...) 不是类型转换。这是一个构造函数调用。

如果你想转换，使用deck.drawRandomCard() as PlayingCard。