Scala 如何使用字符串常量创建枚举

我有一个scopt解析器，它接受颜色参数（“绿色”、“红色”、“蓝色”）。我想把字符串常量放在enum中，你们能帮我写它并把它放在项目中最好的地方吗（可能是package.scala）

---

这实际上在中进行了描述。只要您的枚举是一个单独的类型，您就可以为它创建

scopt.Read

// enumeration
object Color extends Enumeration {
  type Color = Value
  val Red, Green, Blue = Value
}
// has to be imported manually as we cannot put it into `Value` companion
implicit val colorRead: scopt.Read[Color.Value] =
  scopt.Read.reads(Color withName _)

---

如果将

color

类型设置为

Config

的

color

字段，隐式

读取[color]

将使您能够解析配置中的

opt[color]

选项。

您尝试了什么？您的enum有什么要求？

// enumeration
object Color extends Enumeration {
  type Color = Value
  val Red, Green, Blue = Value
}
// has to be imported manually as we cannot put it into `Value` companion
implicit val colorRead: scopt.Read[Color.Value] =
  scopt.Read.reads(Color withName _)

// enumeratum
sealed trait Color EnumEntry
object Color extends Enum[Color] {
  case object Red extends Color
  case object Green extends Color
  case object Blue extends Color
  val values = findValues

  implicit val colorRead: scopt.Read[Color] =
    scopt.Read.reads(Color withName _)
}

// normal sealed trait
sealed trait Color EnumEntry
object Color extends Enum[Color] {
  case object Red extends Color
  case object Green extends Color
  case object Blue extends Color

  implicit val colorRead: scopt.Read[Color] =
    scopt.Read.reads {
      case "green" => Color.Green
      case "red"   => Color.Red
      case "blue"  => Color.Blue
    }
}