嵌套枚举

你可以将枚举嵌套在另一个内部，这样你就可以构建层次结构的枚举，使其更有条理，更清晰。

enum Orchestra {
    enum Strings {
        case violin
        case viola
        case cello
        case doubleBasse
    }
    
    enum Keyboards {
        case piano
        case celesta
        case harp
    }
    
    enum Woodwinds {
        case flute
        case oboe
        case clarinet
        case bassoon
        case contrabassoon
    }
}

你可以像这样使用它：

let instrment1 = Orchestra.Strings.viola
let instrment2 = Orchestra.Keyboards.piano