Swift:将enum值转换为字符串?

Given the following enum:

鉴于以下枚举:

enum Audience {
    case Public
    case Friends
    case Private
}

How do I get the string "Public" from the audience constant below?

如何从下面的观众常数中获得字符串“Public”?

let audience = Audience.Public

11 个解决方案

#1

Not sure in which Swift version this feature was added, but right now (Swift 2.1) you only need this code:

不确定在哪个Swift版本中添加了这个特性，但是现在(Swift 2.1)您只需要这段代码:

enum Audience: String {
    case Public
    case Friends
    case Private
}

let audience = Audience.Public.rawValue // "Public"

When strings are used for raw values, the implicit value for each case is the text of that case’s name.

当字符串用于原始值时，每个case的隐式值都是该case名称的文本。

[...]

[…]

enum CompassPoint: String {
    case North, South, East, West
}

In the example above, CompassPoint.South has an implicit raw value of "South", and so on.

在上面的示例中，是围绕spoint。南方有一个隐含的“南方”的原始价值，等等。

You access the raw value of an enumeration case with its rawValue property:

使用其rawValue属性访问枚举案例的原始值:

let sunsetDirection = CompassPoint.West.rawValue
// sunsetDirection is "West"

Source.

源。

#2

The idiomatic interface for 'getting a String' is to use the CustomStringConvertible interface and access the description getter. Define your enum as:

用于“获取字符串”的惯用接口是使用customconvertible接口并访问description getter。你的枚举定义为:

enum Foo : CustomStringConvertible {
  case Bing
  case Bang
  case Boom

  var description : String { 
    switch self {
    // Use Internationalization, as appropriate.
    case .Bing: return "Bing"
    case .Bang: return "Bang"
    case .Boom: return "Boom"
    }
  }
}

In action:

在行动:

 > let foo = Foo.Bing
foo: Foo = Bing
 > println ("String for 'foo' is \(foo)"
String for 'foo' is Bing

Updated: For Swift >= 2.0, replaced Printable with CustomStringConvertible

更新:对于Swift >= 2.0，用可定制的stringconvertible替换可打印

#3

For now, I'll redefine the enum as:

现在，我将把enum重新定义为:

enum Audience: String {
    case Public = "Public"
    case Friends = "Friends"
    case Private = "Private"
}

so that I can do:

我可以这样做:

audience.toRaw() // "Public"

But, isn't this new enum definition redundant? Can I keep the initial enum definition and do something like:

但是，新的enum定义不是多余的吗?我可以保留初始的enum定义吗?

audience.toString() // "Public"

#4

I like to use Printable with Raw Values.

我喜欢使用可打印的原始值。

enum Audience: String, Printable {
    case Public = "Public"
    case Friends = "Friends"
    case Private = "Private"

    var description: String {
        return self.rawValue
    }
}

Then we can do:

然后我们能做什么:

let audience = Audience.Public.description // audience = "Public"

or

或

println("The value of Public is \(Audience.Public)") 
// Prints "The value of Public is Public"

#5

In swift 3, you can use this

在swift 3中，您可以使用这个

var enumValue = Customer.Physics
var str = String(describing: enumValue)

from Swift how to use enum to get string value

从如何使用enum获取字符串值

#6

Updated for the release of Xcode 7 GM. It works as one would hope now--thanks Apple!

为Xcode 7 GM的发布而更新。它现在可以像人们希望的那样工作了——谢谢苹果!

enum Rank:Int {
    case Ace = 1, Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Jack, Queen, King
}

let r = Rank.Ace

print(r)               // prints "Ace"
print("Rank: \(r)!")   // prints "Rank: Ace!"

#7

It couldn't get simpler than this in Swift 2 and the latest Xcode 7 (no need to specify enum type, or .rawValue, descriptors etc...)

在Swift 2和最新的Xcode 7中(不需要指定enum类型，或.rawValue、descriptors等等)，这一点再简单不过了。

Updated for Swift 3 and Xcode 8:

Swift 3和Xcode 8更新:

    enum Audience {
        case Public
        case Friends
        case Private
    }

    let audience: Audience = .Public  // or, let audience = Audience.Public
    print(audience) // "Public"

#8

There are multiple ways to do this. Either you could define a function in the enum which returns the string based on the value of enum type:

有多种方法可以做到这一点。您可以在enum中定义一个函数，该函数根据enum类型的值返回字符串:

enum Audience{
    ...
func toString()->String{
  var a:String

  switch self{
   case .Public:
    a="Public"
   case .Friends:
    a="Friends"
   ...
 }
 return a
}

Or you could can try this:

或者你可以试试这个:

enum Audience:String{
   case Public="Public"
   case Friends="Friends"
   case Private="Private"
}

And to use it:

和使用它:

var a:Audience=Audience.Public
println(a.toRaw())

#9

For anyone reading the example in "A Swift Tour" chapter of "The Swift Programming Language" and looking for a way to simplify the simpleDescription() method, converting the enum itself to String by doing String(self) will do it:

对于任何在“Swift编程语言”章节中阅读示例的人，并寻找简化simpleDescription()方法的方法，将枚举本身转换为字符串(self)将会这样做:

  enum Rank: Int
  {
    case Ace = 1 //required otherwise Ace will be 0
    case Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten
    case Jack, Queen, King
    func simpleDescription() -> String {
        switch self {
            case .Ace, .Jack, .Queen, .King:
                return String(self).lowercaseString
            default:
                return String(self.rawValue)
        }
     }
   }

#10

After try few different ways, i found that if you don't want to use:

在尝试了几种不同的方法后，我发现如果你不想用:

let audience = Audience.Public.toRaw()

You can still archive it using a struct

您仍然可以使用struct对其进行存档

struct Audience {
   static let Public  = "Public"
   static let Friends = "Friends"
   static let Private = "Private"
}

then your code:

那么你的代码:

let audience = Audience.Public

will work as expected. It isn't pretty and there are some downsides because you not using a "enum", you can't use the shortcut only adding .Private neither will work with switch cases.

将按预期工作。它并不漂亮，而且也有一些缺点，因为您没有使用“enum”，您不能使用仅添加. private的快捷方式，也不能使用switch case。

#11

A swift 3 and above example if using Ints in Enum

如果在Enum中使用Ints，可以使用swift 3和以上示例

public enum ECategory : Int{
        case Attraction=0, FP, Food, Restroom, Popcorn, Shop, Service, None;
        var description: String {
            return String(describing: self)
        }
    }

let category = ECategory.Attraction
let categoryName = category.description //string Attraction