Question

我有一个简单的字符串类型枚举：

enum MyEnum: String {
    case hello = "hello"
    case world = "world"
}

我想写一个不区分大小写的构造函数。我尝试了这个（带有或不带有扩展名）：

init?(string: String) {
    return self.init(rawValue: string.lowercased())
}

但我收到一条错误消息：

'nil' is the only value permitted in an initializer

Answer 1

您不需要return。您只需调用初始值设定项即可：

enum MyEnum: String {
    case hello = "hello"
    case world = "world"

    init?(caseInsensitive string: String) {
        self.init(rawValue: string.lowercased())
    }
}

print(MyEnum(caseInsensitive: "HELLO") as Any) // => Optional(Untitled.MyEnum.hello)
print(MyEnum(caseInsensitive: "Goodbye") as Any) // => nil

使用自定义构造函数的Swift枚举

1 个答案: