Scala safe way of converting String to Enumeration value

Question

Suppose I have enumeration:

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

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

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

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

Shadowlands · Accepted Answer · 2015-11-08 11:53:31Z

61

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

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

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

answered Nov 8, 2015 at 11:53

Shadowlands

15.1k4 gold badges47 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Nader Ghanbari Over a year ago

Wish this was part of the standard library, it's idiomatic Scala after all to have a safe way of doing things.

monksy Over a year ago

Might want to consider doing a case-insensitive comparison check

Jeffrey Tillwick Over a year ago

Doesn't work since Java 9. _ can no longer be used as an identifier.

Bhuvan Singla · Accepted Answer · 2021-02-12 00:52:44Z

11

Building on top of @Shadowlands 's answer, I added this method to my enum to have a default Unknown value without dealing with options:

def withNameWithDefault(name: String): Value =
  values.find(_.toString.toLowerCase() == name.toLowerCase()).getOrElse(Unknown)

so the enum would look like this:

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

  def withNameWithDefault(name: String): Value = 
    values.find(_.toString.toLowerCase() == name.toLowerCase()).getOrElse(Unknown)
}

edited Feb 12, 2021 at 0:52

Bhuvan Singla

236 bronze badges

answered Aug 5, 2017 at 10:21

Javad

6,0464 gold badges44 silver badges52 bronze badges

Collectives™ on Stack Overflow

Scala safe way of converting String to Enumeration value

2 Answers 2

3 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related