CODEWITHSUNDEEP
scala
randombits
randombits

Reputation: 48460

What does `var @ _*` signify in Scala

I'm reviewing some Scala code trying to learn the language. Ran into a piece that looks like the following:

 case x if x startsWith "+" => 
          val s: Seq[Char] = x
          s match {
            case Seq('+', rest @ _*) => r.subscribe(rest.toString){ m => }
          }

In this case, what exactly is rest @ _* doing? I understand this is a pattern match for a Sequence, but I'm not exactly understanding what that second parameter in the Sequence is supposed to do.

Was asked for more context so I added the code block I found this in.

Upvotes: 1

Views: 207

Answers (2)

Shadowlands
Shadowlands

Reputation: 15074

If you have come across _* before in the form of applying a Seq as varargs to some method/constructor, eg:

val myList = List(args: _*)

then this is the "unapply" (more specifically, search for "unapplySeq") version of this: take the sequence and convert back to a "varargs", then assign the result to rest.

Upvotes: 5

Jon Purdy
Jon Purdy

Reputation: 54999

x @ p matches the pattern p and binds the result of the whole match to x. This pattern matches a Seq containing '+' followed by any number (*) of unnamed elements (_) and binds rest to a Seq of those elements.

Upvotes: 2

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