enum Suit: String { case spades = "♠" case hearts = "♥" case diamonds = "♦" case clubs = "♣" }
例如,我该怎么做:
for suit in Suit { // do something with suit print(suit.rawValue) }
结果示例:
♠ ♥ ♦ ♣
从Swift 4.2(使用Xcode 10)开始,只需添加协议一致性CaseIterable即可从中受益allCases。要添加此协议一致性,您只需要在某处写:
CaseIterable
allCases
extension Suit: CaseIterable {}
如果枚举是您自己的,则可以直接在声明中指定一致性:
enum Suit: String, CaseIterable { case spades = "♠"; case hearts = "♥"; case diamonds = "♦"; case clubs = "♣" }
然后,以下代码将打印所有可能的值:
Suit.allCases.forEach { print($0.rawValue) }
如果您需要支持Swift 3.x或4.0,则可以通过添加以下代码来模仿Swift 4.2的实现:
#if !swift(>=4.2) public protocol CaseIterable { associatedtype AllCases: Collection where AllCases.Element == Self static var allCases: AllCases { get } } extension CaseIterable where Self: Hashable { static var allCases: [Self] { return [Self](AnySequence { () -> AnyIterator<Self> in var raw = 0 var first: Self? return AnyIterator { let current = withUnsafeBytes(of: &raw) { $0.load(as: Self.self) } if raw == 0 { first = current } else if current == first { return nil } raw += 1 return current } }) } } #endif