Question

我正在做一个Swift编程书的实验，并坚持在struct本身内部构造一个struct。但错误报告参数已解包。我怎么能把它作为参数值？

struct Card {
    var rank: Rank
    var suit: Suit
    func simpleDescription() -> String {
        return "The \(rank.simpleDescription()) of \(suit.simpleDescription())"
    }
    func FullDeck() -> Card[] {
        var deck: Card[]
        for i in 1...13
        {
            for j in 0...3
            {
                let rank_para = Rank.fromRaw(i)
                let suit_para = Suit.fromRaw(j)


                **deck.append(Card(rank: rank_para, suit : suit_para ))
                //value of optional type unwrapped;did you mean to use ? or !**

            }
        }
        return deck
    }
}




enum Rank: Int {
    case Ace = 1
    case Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten
    case Jack, Queen, King
    func simpleDescription() -> String {
        switch self {
        case .Ace:
            return "ace"
        case .Jack:
            return "jack"
        case .Queen:
            return "queen"
        case .King:
            return "king"
        default:
            return String(self.toRaw())
        }
    }
    func compare(sec:Rank) -> Bool {
        var first = 0
        var second = 0
        if self.toRaw() == 1 {
            first = 1
        } else {
            first = self.toRaw()
        }
        if sec.toRaw() == 1 {
            second = 1
        } else {
            second = self.toRaw()
        }
        return first > second
    }
}


enum Suit: Int{
    case Spades = 0
    case Hearts, Diamonds, Clubs
    func simpleDescription() -> String {
        switch self {
        case .Spades:
            return "spades"
        case .Hearts:
            return "hearts"
        case .Diamonds:
            return "diamonds"
        case .Clubs:
            return "clubs"
        }
    }
}

Answer 1

fromRaw方法返回一个可选值：Rank?和Suit?。这意味着价值可能是零。你需要检查一下：

if let aRank = rank_para {
    if let aSuit = suit_para {
        deck.append(Card(rank: aRank, suit: aSuit))
    }
}

使用＆＃34;如果让＆＃34;，你＆＃34;打开＆＃34;可选值为值（aRank和aSuit），不再是可选的（不能为零）。

另一种方法：

if rank_para and suit_para {
    deck.append(Card(rank: rank_para!, suit: suit_para!))
}

在这里，您正在检查rank_para和suit_para是否为零。如果两者都没有，你打电话给追加和＆＃34;打开＆＃34;使用!的可选值。 !表示如果值nil抛出运行时错误，则将此变量视为不能nil。

swift如何在构造struct时使用enum作为参数？

1 个答案:

另一种方法：