Scala Language Option


Example

The use of null values is strongly discouraged, unless interacting with legacy Java code that expects null. Instead, Option should be used when the result of a function might either be something (Some) or nothing (None).

A try-catch block is more appropriate for error-handling, but if the function might legitimately return nothing, Option is appropriate to use, and simple.

An Option[T] can either be Some(value) (contains a value of type T) or None:

def findPerson(name: String): Option[Person]

If no person is found, None can be returned. Otherwise, an object of type Some containing a Person object is returned. What follows are ways to handle an object of type Option.

Pattern Matching

findPerson(personName) match {
    case Some(person) => println(person.surname)
    case None => println(s"No person found with name $personName")
}

Using map and getOrElse

val name = findPerson(personName).map(_.firstName).getOrElse("Unknown")
println(name) // Prints either the name of the found person or "Unknown"

Using fold

val name = findPerson(personName).fold("Unknown")(_.firstName)
// equivalent to the map getOrElse example above.

Converting to Java

If you need to convert an Option type to a null-able Java type for interoperability:

val s: Option[String] = Option("hello")
s.orNull           // "hello": String
s.getOrElse(null)  // "hello": String

val n: Option[Int] = Option(42)
n.orNull           // compilation failure (Cannot prove that Null <:< Int.)
n.getOrElse(null)  // 42