在 Swift 中，是否可以将字符串转换为枚举? [英] In Swift, is it possible to convert a string to an enum?

问题描述

如果我有一个包含 a,b,c,d 的枚举，是否可以将字符串a"转换为枚举?

If I have an enum with the cases a,b,c,d is it possible for me to cast the string "a" as the enum?

推荐答案

好的.枚举可以具有原始值.引用文档:

Sure. Enums can have a raw value. To quote the docs:

原始值可以是字符串、字符或任何整数或浮点数类型

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

——摘自:Apple Inc.The Swift Programming Language".电子书.https://itun.es/us/jEUH0.l,

— Excerpt From: Apple Inc. "The Swift Programming Language." iBooks. https://itun.es/us/jEUH0.l,

所以你可以使用这样的代码:

So you can use code like this:

enum StringEnum: String 
{
    case one   = "value one"
    case two   = "value two"
    case three = "value three"
}

let anEnum = StringEnum(rawValue: "value one")!

print("anEnum = "(anEnum.rawValue)"")

注意:你不需要写 = one";等等.在每个案例之后.默认字符串值与案例名称相同，因此调用 .rawValue 只会返回一个字符串

Note: You don't need to write = "one" etc. after each case. The default string values are the same as the case names so calling .rawValue will just return a string

如果您需要字符串值包含不能作为 case 值一部分的空格之类的东西，那么您需要显式设置字符串.所以，

If you need the string value to contain things like spaces that are not valid as part of a case value then you need to explicitly set the string. So,

enum StringEnum: String 
{
  case one
  case two
  case three
}

let anEnum = StringEnum.one
print("anEnum = "(anEnum)"")

给予

anEnum = 一个"

anEnum = "one"

但是如果你想让 case one 显示值一"您需要提供字符串值:

But if you want case one to display "value one" you will need to provide the string values:

enum StringEnum: String 
{
  case one   = "value one"
  case two   = "value two"
  case three = "value three"
}

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