Swift 5.1 (18) - 嵌套類型

級別: ★☆☆☆☆
標籤:「iOS」「Swift 5.1 」「嵌套類型」
做者: 沐靈洛
審校: QiShare團隊
php


Swift容許定義嵌套類型,在它們所支持類型的定義中支持嵌套枚舉,類和結構。類型能夠嵌套到所需的級別。git

嵌套類型使用

struct BlackjackCard {

    // nested Suit enumeration
    enum Suit: Character {
        case spades = "♠", hearts = "♡", diamonds = "♢", clubs = "♣"
    }

    // nested Rank enumeration
    enum Rank: Int {
        case two = 2, three, four, five, six, seven, eight, nine, ten
        case jack, queen, king, ace
        struct Values {
            let first: Int, second: Int?
        }
        var values: Values {
            switch self {
            case .ace:
                return Values(first: 1, second: 11)
            case .jack, .queen, .king:
                return Values(first: 10, second: nil)
            default:
                return Values(first: self.rawValue, second: nil)
            }
        }
    }

    // BlackjackCard properties and methods
    let rank: Rank, suit: Suit
    var description: String {
        var output = "suit is \(suit.rawValue),"
        output += " value is \(rank.values.first)"
        if let second = rank.values.second {
            output += " or \(second)"
        }
        return output
    }
}
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###嵌套類型的引用github

let heartsSymbol = BlackjackCard.Suit.hearts.rawValue
// heartsSymbol is "♡"
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