enum StringCase:String {
    case One = "One"
    case Two,Three,Four,Five
    
    func discription() -> String {
        switch self {
        case .One:
            return "One"
        case .Two:
            return "Two"
        case .Three:
            return "Three"
        case .Four:
            return "Four"
        case .Five:
            return "Five"
        }
    }
}

下面的写法是错误的，编译会报错，因为switch没有所有的case做出列举，需要添加default分支

enum StringCase:String {
    case One = "One"
    case Two,Five
    
    func discription() -> String {
        switch self {
        case .One:
            return "One"
        case .Two:
            return "Two"
        case .Three:
            return "Three"
        case .Four:
            return "Four"
        }
    }
}