http://www.scala-lang.org/docu/files/api/scala/Enumeration.html

示例使用

  object Main extends App {

    object WeekDay extends Enumeration {
      type WeekDay = Value
      val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value
    }
    import WeekDay._

    def isWorkingDay(d: WeekDay) = ! (d == Sat || d == Sun)

    WeekDay.values filter isWorkingDay foreach println
  }

声明命名枚举的一种稍微不那么冗长的方式:

object WeekDay extends Enumeration("Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat") {
  type WeekDay = Value
  val Sun, Mon, Tue, Wed, Thu, Fri, Sat = Value
}

WeekDay.valueOf("Wed") // returns Some(Wed)
WeekDay.Fri.toString   // returns Fri

当然，这里的问题是，您需要保持name和val的顺序同步，如果name和val声明在同一行上，这将更容易做到。

在Scala中，https://github.com/lloydmeta/enumeratum非常适合

项目是非常好的例子和文档

他们文档中的这个例子应该会让你感兴趣

import enumeratum._

sealed trait Greeting extends EnumEntry

object Greeting extends Enum[Greeting] {

  /*
   `findValues` is a protected method that invokes a macro to find all `Greeting` object declarations inside an `Enum`

   You use it to implement the `val values` member
  */
  val values = findValues

  case object Hello   extends Greeting
  case object GoodBye extends Greeting
  case object Hi      extends Greeting
  case object Bye     extends Greeting

}

// Object Greeting has a `withName(name: String)` method
Greeting.withName("Hello")
// => res0: Greeting = Hello

Greeting.withName("Haro")
// => java.lang.IllegalArgumentException: Haro is not a member of Enum (Hello, GoodBye, Hi, Bye)

// A safer alternative would be to use `withNameOption(name: String)` method which returns an Option[Greeting]
Greeting.withNameOption("Hello")
// => res1: Option[Greeting] = Some(Hello)

Greeting.withNameOption("Haro")
// => res2: Option[Greeting] = None

// It is also possible to use strings case insensitively
Greeting.withNameInsensitive("HeLLo")
// => res3: Greeting = Hello

Greeting.withNameInsensitiveOption("HeLLo")
// => res4: Option[Greeting] = Some(Hello)

// Uppercase-only strings may also be used
Greeting.withNameUppercaseOnly("HELLO")
// => res5: Greeting = Hello

Greeting.withNameUppercaseOnlyOption("HeLLo")
// => res6: Option[Greeting] = None

// Similarly, lowercase-only strings may also be used
Greeting.withNameLowercaseOnly("hello")
// => res7: Greeting = Hello

Greeting.withNameLowercaseOnlyOption("hello")
// => res8: Option[Greeting] = Some(Hello)

从Scala 3开始，现在有一个enum关键字，它可以表示一组常量(和其他用例)

enum Color:
   case Red, Green, Blue

scala> val red = Color.Red
val red: Color = Red
scala> red.ordinal
val res0: Int = 0

我必须说，上面skaffman从Scala文档中复制的示例在实践中用处有限(您还可以使用case对象)。

为了获得最接近Java Enum的东西(即使用合理的toString和valueOf方法——也许你要将枚举值持久化到数据库中)，你需要稍微修改它。如果你使用skaffman的代码:

WeekDay.valueOf("Sun") //returns None
WeekDay.Tue.toString   //returns Weekday(2)

鉴于使用以下声明:

object WeekDay extends Enumeration {
  type WeekDay = Value
  val Mon = Value("Mon")
  val Tue = Value("Tue") 
  ... etc
}

你会得到更合理的结果:

WeekDay.valueOf("Sun") //returns Some(Sun)
WeekDay.Tue.toString   //returns Tue

http://www.scala-lang.org/docu/files/api/scala/Enumeration.html

示例使用

  object Main extends App {

    object WeekDay extends Enumeration {
      type WeekDay = Value
      val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value
    }
    import WeekDay._

    def isWorkingDay(d: WeekDay) = ! (d == Sat || d == Sun)

    WeekDay.values filter isWorkingDay foreach println
  }