Swift - 繼承自該類的Cast對象

Question

我收到此錯誤：無法將表達式的類型'（）'轉換爲鍵入$'T5' Card從CardCard繼承，並且我知道drawRandomCard返回了一個PlayingCard。 如何進行此轉換？

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) 
    } 
} 

} 

上git的全碼：https://github.com/victoryudi/CS193p-Swift/tree/master/FlipCard

Answer 1

PlayingCard(...)不是一個演員。這是一個構造函數調用。

如果要投射，請使用deck.drawRandomCard() as PlayingCard。