将字符串转换为枚举值的 Scala 安全方法 [英] Scala safe way of converting String to Enumeration value

问题描述

假设我有枚举:

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

我希望能够将 String 转换为 WeekDay 值，这很好:

I would like to be able to convert String to WeekDay value and this is fine with:

scala> WeekDay.withName("Tue")
res10: WeekDay.Value = Tue

但是，如果我传递了一些未知"值，则会出现异常:

But if I pass some 'unknown' value, I'm getting exception:

scala> WeekDay.withName("Ou")
java.util.NoSuchElementException: None.get
  at scala.None$.get(Option.scala:322)
  at scala.None$.get(Option.scala:320)
  at scala.Enumeration.withName(Enumeration.scala:124)
  ... 32 elided

是否有一些优雅的方法可以安全地将字符串转换为枚举值?

Is there some elegant way of safely convert String to Enumeration value?

推荐答案

你可以在枚举中添加一个方法来返回一个Option[Value]:

You can add a method to the enumeration to return an Option[Value]:

def withNameOpt(s: String): Option[Value] = values.find(_.toString == s)

注意:现有的 withName 方法实际上就是这样做的，然后调用 getOrElse 在else"情况下抛出异常.

Note: the existing withName method actually does precisely this, then calls getOrElse throwing the exception in the "else" case.

这篇关于将字符串转换为枚举值的 Scala 安全方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！