Question

是否可以在Swift中循环枚举值？或者替代方案是什么？

我正在使用Apple的Swift语言指南，我在枚举时遇到了这个例子。

//  EXPERIMENT
//
//  Add a method to Card that creates a full deck of cards, 
//  with one card of each combination of rank and suit.

struct Card {
    var rank: Rank
    var suit: Suit
    func simpleDescription() -> String {
        return "The \(rank.simpleDescription()) of \(suit.simpleDescription())"
    }
}
let threeOfSpades = Card(rank: .Three, suit: .Spades)
let threeOfSpadesDescription = threeOfSpades.simpleDescription()

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

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())
        }
    }
}

摘自：Apple Inc.“The Swift Programming Language。”iBooks。 https://itun.es/us/jEUH0.l

我已经尝试了以下内容，但文档说Swift中的枚举没有像C中那样分配基础整数值，所以我可能会咆哮错误的树。

有没有更好的方法来解决这个问题？

func deck() -> Card[]{
    var deck: Card[]
    for s in Suit {
        for r in Rank {
            deck += Card(rank: r, suit: s)
        }
    }
    return deck
}

func deck2() -> Card[]{
    var deck: Card[]
    for var s: Suit = .Spades; s <= .Clubs; s++ {
        for var r: Rank = .Ace; r <= .King; r++ {
            deck += Card(rank: r, suit: s)
        }
    }
    return deck
}

Answer 1

还有其他方法吗？当然。是更好，这是由你来决定的：

func generateDeck() -> Card[]
{
    let ranksPerSuit = 13
    var deck = Card[]()

    for index in 0..52
    {
        let suit = Suit.fromRaw(index / ranksPerSuit)
        let rank = Rank.fromRaw(index % ranksPerSuit + 1)

        let card = Card(rank: rank!, suit: suit!)
        deck.append(card)
    }

    return deck
}

let deck = generateDeck()

for card : Card in deck { println("\(card.description)") }

要使用此功能，您需要确保Rank和Suit枚举使用Int作为其类型定义（例如：enum Rank : Int）。

Rank.Ace应该等于1，并且第一个Suit案例应该等于0。

如果您想循环类似于现有代码，您仍应使用枚举Int类型，以便使用Rank.King.toRaw()等。

Apple文档声明枚举并不仅限于“简单整数值”，但如果您希望枚举，肯定可以。

<强>更新

来自@ jay-imerman评论的想法，适用于Swift 5

extension Rank: CaseIterable {}
extension Suit: CaseIterable {}

func generateDeck() -> [Card] {
    var deck = [Card]();

    Rank.allCases.forEach {
        let rank = $0

        Suit.allCases.forEach {
            let suit = $0

            deck.append(Card(rank: rank, suit: suit))
        }
    }

    return deck;
}

循环遍历Swift中的枚举值

1 个答案: