CODEWITHSUNDEEP
scalaf#
Jas
Jas

Reputation: 15113

Combining types in scala

I saw that in F# its very easy to define a type which is a combined from a set of other types such as

type MyFiveNumbers = One | Two | Three | Four | Five

This looks just great!

What is the simplest way to do that in Scala?

Upvotes: 1

Views: 136

Answers (1)

Alexey Romanov
Alexey Romanov

Reputation: 170805

One and the rest are not types, but union cases. The Scala equivalent in fact does make them types:

sealed trait MyFiveNumbers

case object One extends MyFiveNumbers

case object Two extends MyFiveNumbers

...

In such a simple case you might be best off just using a Java enum. However, if any constructors have parameters (e.g. add | Other of int to the end), they correspond to Scala case classes:

case class Other(x: Int) extends MyFiveNumbers

You can use pattern matching just as in F#:

// x has type MyFiveNumbers
x match {
  case One => ...
  ...
  case Other(n) => ...
}

and get compiler warnings about incomplete matches (only if the sealed keyword is used; otherwise you can create additional cases in other files).

Upvotes: 5

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