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

如果我有一个枚举与案例a，b，c，d可以将字符串a作为枚举？

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

当然可以。枚举可以有一个原始值。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

- 摘录自：Apple Inc.Swift编程语言iBooks。 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 = "one"
  case two = "two"
  case three = "three"
}

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

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

注意：在每种情况下，您不需要写=一等。默认字符串值与案例名称相同，因此调用 .rawValue 将返回一个字符串

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以包含作为案例值一部分无效的空格，则需要显式设置字符串。因此，

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

anEnum =one

anEnum = "one"

但是，如果你想要 case / code>显示value one，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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