Scala: Expand List of Tuples into variable-length argument list of Tuples

Question

I'm puzzled on how to expand List/Seq/Array into variable-length argument list.

Given that I have test_func function accepting tuples:

scala> def test_func(t:Tuple2[String,String]*) = println("works!")
test_func: (t: (String, String)*)Unit

Which works when I pass tuples:

scala> test_func(("1","2"),("3","4"))
works!

From reading the Scala reference I've got strong impression that the following whould work as well:

scala> test_func(List(("1","2"),("3","4")))
<console>:9: error: type mismatch;
 found   : List[(java.lang.String, java.lang.String)]
 required: (String, String)
              test_func(List(("1","2"),("3","4")))
                        ^

And one more desperate attempt:

scala> test_func(List(("1","2"),("3","4")).toSeq)
<console>:9: error: type mismatch;
 found   : scala.collection.immutable.Seq[(java.lang.String, java.lang.String)]
 required: (String, String)
              test_func(List(("1","2"),("3","4")).toSeq)

How to expand List/Seq/Array into argument list?

Thank you in advance!

Answer 1

You need to add :_*.

scala> test_func(List(("1","2"),("3","4")):_*)
works!
scala> test_func(Seq(("1","2"),("3","4")):_*)
works!
scala> test_func(Array(("1","2"),("3","4")):_*)
works!