具有原始值的枚举

Question

为什么我不能用这样的原始值定义枚举？

enum Edges : (Double, Double) {
    case TopLeft = (0.0, 0.0)
    case TopRight = (1.0, 0.0)
    case BottomLeft = (0.0, 1.0)
    case BottomRight = (1.0, 1.0)
}

Answer 1

Because:

Raw values can be strings, characters, or any of the integer or floating-point number types.

但是有一个替代解决方案适合您：

enum Edges {
    case TopLeft
    case TopRight
    case BottomLeft
    case BottomRight

    func getTuple() -> (Double, Double) {
        switch self {
        case .TopLeft:
            return (0.0, 0.0)
        case .TopRight:
            return (1.0, 0.0)
        case .BottomLeft:
            return (0.0, 1.0)
        case .BottomRight:
            return (1.0, 1.0)
        }
    }
}

let a = Edges.BottomLeft
a.getTuple() // returning (0, 1)

Answer 2

元组不能是枚举的原始值类型。来自 The Swift Programming Language:

Raw values can be strings, characters, or any of the integer or floating-point number types.

不过您可以创建自定义 getter：

enum Edges {
    case TopLeft, TopRight, BottomLeft, BottomRight

    var rawValue: (Double, Double) {
        switch self {
            case .TopLeft: return (0, 0)
            case .TopRight: return (1, 0)
            case .BottomLeft: return (0, 1)
            case .BottomRight: return (1, 1)
        }
    }
}

具有原始值的枚举

Enumeration with raw values

swift

rawrepresentable