CODEWITHSUNDEEP
scala
Nyavro
Nyavro

Reputation: 8866

Scala safe way of converting String to Enumeration value

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?

Upvotes: 38

Views: 35838

Answers (2)

Javad
Javad

Reputation: 6016

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)
}

Upvotes: 11

Shadowlands
Shadowlands

Reputation: 15074

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.

Upvotes: 61

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