从Xcode 7 beta 5 (Swift版本2)开始，你现在可以默认使用print(_:)打印类型名和enum大小写，或者使用String的init(_:)初始化器或字符串插值语法转换为String。举个例子:

enum City: Int {
    case Melbourne = 1, Chelyabinsk, Bursa
}
let city = City.Melbourne

print(city)
// prints "Melbourne"

let cityName = "\(city)"   // or `let cityName = String(city)`
// cityName contains "Melbourne"

因此，不再需要定义和维护一个方便的函数来切换每个大小写以返回字符串字面量。此外，即使没有指定原始值类型，它也会自动适用于任何枚举。

debugPrint(_:) & String(reflection:)可以用于完全限定名:

debugPrint(city)
// prints "App.City.Melbourne" (or similar, depending on the full scope)

let cityDebugName = String(reflecting: city)
// cityDebugName contains "App.City.Melbourne"

请注意，您可以自定义在这些场景中打印的内容:

extension City: CustomStringConvertible {
    var description: String {
        return "City \(rawValue)"
    }
}

print(city)
// prints "City 1"

extension City: CustomDebugStringConvertible {
    var debugDescription: String {
        return "City (rawValue: \(rawValue))"
    }
}

debugPrint(city)
// prints "City (rawValue: 1)"

(我还没有找到一种方法来调用这个“默认”值，例如，打印“城市是墨尔本”而不求助于switch语句。在description/debugDescription的实现中使用\(self)会导致无限递归。)

String的init(_:)和init(reflections:)初始化器上面的注释描述了打印的内容，具体取决于反射的类型:

extension String {
    /// Initialize `self` with the textual representation of `instance`.
    ///
    /// * If `T` conforms to `Streamable`, the result is obtained by
    ///   calling `instance.writeTo(s)` on an empty string s.
    /// * Otherwise, if `T` conforms to `CustomStringConvertible`, the
    ///   result is `instance`'s `description`
    /// * Otherwise, if `T` conforms to `CustomDebugStringConvertible`,
    ///   the result is `instance`'s `debugDescription`
    /// * Otherwise, an unspecified result is supplied automatically by
    ///   the Swift standard library.
    ///
    /// - SeeAlso: `String.init<T>(reflecting: T)`
    public init<T>(_ instance: T)

    /// Initialize `self` with a detailed textual representation of
    /// `subject`, suitable for debugging.
    ///
    /// * If `T` conforms to `CustomDebugStringConvertible`, the result
    ///   is `subject`'s `debugDescription`.
    ///
    /// * Otherwise, if `T` conforms to `CustomStringConvertible`, the result
    ///   is `subject`'s `description`.
    ///
    /// * Otherwise, if `T` conforms to `Streamable`, the result is
    ///   obtained by calling `subject.writeTo(s)` on an empty string s.
    ///
    /// * Otherwise, an unspecified result is supplied automatically by
    ///   the Swift standard library.
    ///
    /// - SeeAlso: `String.init<T>(T)`
    public init<T>(reflecting subject: T)
}

有关此更改的信息，请参阅发布说明。

在Swift-3(用Xcode 8.1测试)中，你可以在你的枚举中添加以下方法:

/**
 * The name of the enumeration (as written in case).
 */
var name: String {
    get { return String(describing: self) }
}

/**
 * The full name of the enumeration
 * (the name of the enum plus dot plus the name as written in case).
 */
var description: String {
    get { return String(reflecting: self) }
}

然后，您可以将其用作枚举实例上的常规方法调用。 它可能也适用于以前的Swift版本，但我还没有测试过。

在你的例子中:

enum City: Int {
    case Melbourne = 1, Chelyabinsk, Bursa
    var name: String {
        get { return String(describing: self) }
    }
    var description: String {
        get { return String(reflecting: self) }
    }
}
let city = City.Melbourne

print(city.name)
// prints "Melbourne"

print(city.description)
// prints "City.Melbourne"

如果你想为你所有的枚举提供这个功能，你可以让它成为一个扩展:

/**
 * Extend all enums with a simple method to derive their names.
 */
extension RawRepresentable where RawValue: Any {
  /**
   * The name of the enumeration (as written in case).
   */
  var name: String {
    get { return String(describing: self) }
  }

  /**
   * The full name of the enumeration
   * (the name of the enum plus dot plus the name as written in case).
   */
  var description: String {
    get { return String(reflecting: self) }
  }
}

这只适用于Swift枚举。

在Swift 2.2中对枚举的String(…)(CustomStringConvertible)支持的基础上，对它们也有一些破碎的反射支持。对于有关联值的枚举案例，可以使用反射获得枚举案例的标签:

enum City {
    case Melbourne(String)
    case Chelyabinsk
    case Bursa

    var label:String? {
        let mirror = Mirror(reflecting: self)
        return mirror.children.first?.label
    }
}

print(City.Melbourne("Foobar").label) // prints out "Melbourne"

然而，我的意思是，对于“简单”枚举，上面基于反射的标签计算属性只返回nil (boo-hoo)。

print(City.Chelyabinsk.label) // prints out nil

显然，在《Swift 3》之后，反思的情况应该会有所好转。现在的解决方案是String(…)，正如在其他答案之一中建议的那样:

print(String(City.Chelyabinsk)) // prints out Cheylabinsk

目前在枚举情况下没有自省。你必须手动声明它们:

enum City: String, CustomStringConvertible {
    case Melbourne = "Melbourne"
    case Chelyabinsk = "Chelyabinsk"
    case Bursa = "Bursa"

    var description: String {
        get {
            return self.rawValue
        }
    }
}

如果你需要原始类型是Int，你必须自己做一个切换:

enum City: Int, CustomStringConvertible {
  case Melbourne = 1, Chelyabinsk, Bursa

  var description: String {
    get {
      switch self {
        case .Melbourne:
          return "Melbourne"
        case .Chelyabinsk:
          return "Chelyabinsk"
        case .Bursa:
          return "Bursa"
      }
    }
  }
}

内省在快速枚举似乎部分工作。

我看到了@drewag的回复，发现一个没有rawValues的Enum确实可以在Swift 5中进行自省。X与Xcode 11.5。这段代码可以工作。

public enum Domain: String {
    case network
    case data
    case service
    case sync
    var description: String {
        return "\(self)"     // THIS INTROSPECTION WORKS
    }
}
enum ErrorCode: Int, CustomStringConvertible {
    case success = 200
    case created = 201
    case accepted = 202
    case badRequest = 400
    case unauthorized = 401
    case forbidden = 403
    case notFound = 404
    var code: Int {
        return self.rawValue
    }
    var description: String {
        return "\(self)"      //THIS DOES NOT WORK - EXEC_BAD_ACCESS
    }
}
let errorCode = ErrorCode.notFound
let domain = Domain.network
print(domain.description, errorCode.code, errorCode.description)

在第二个Enum中，将"\(self)"替换为"string"，你将得到以下打印输出: 网络404字符串

注意:在第一个枚举中使用String(self)而不是"\(self)"将要求Enum符合theLosslessStringConvertible '协议，并添加其他初始化器，因此字符串插值似乎是一个很好的解决方案。

要将var description: String添加到枚举中，您必须使用Switch语句将前面指出的所有枚举情况

var description: String {
    switch self {
    case .success: return "Success"
    case .created: return "Created"
    case .accepted: return "Accepted"
    }
}

迅速:

extension UIDeviceBatteryState: CustomStringConvertible {

    public var description: String {
        switch self {
        case .unknown:
            return "unknown"
        case .unplugged:
            return "unplugged"
        case .charging:
            return "charging"
        case .full:
            return "full"
        }
    }

}

如果你的变量是“batteryState”，那么调用:

self.batteryState.description