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arraysscalavariadic-functions
Cherry
Cherry

Reputation: 33534

How to pass Scala array into Scala vararg method?

Consider the code below:

private def test(some:String*){

}

private def call () {
  val some = Array("asd", "zxc")
  test(some)
}

It prints expect String, found Array[String] Why? Are Scala varargs not arrays?

Note

I found several questions on Stack Overflow about Scala varargs, but all of them are about calling Java varargs methods or about converting Scala lists to arrays.

Upvotes: 96

Views: 47238

Answers (3)

Saurav Sahu
Saurav Sahu

Reputation: 13924

Starting Scala 2.13.0, if you use some: _*, you will get this warning:

Passing an explicit array value to a Scala varargs method is deprecated (since 2.13.0) and will result in a defensive copy; Use the more efficient non-copying ArraySeq.unsafeWrapArray or an explicit toIndexedSeq call

As suggested, use scala.collection.immutable.ArraySeq.unsafeWrapArray:

unsafeWrapArray(some):_*

Also, another warning that you should be getting is this one

procedure syntax is deprecated: instead, add : Unit = to explicitly declare test's return type

To fix that, add = just before function's opening bracket:

def test(some:String*) = {

Upvotes: 7

Herrington Darkholme
Herrington Darkholme

Reputation: 6315

It is simple:

def test(some:String*){}

def call () {
  val some = Array("asd", "zxc")
  test(some: _*)
}

Upvotes: 50

Yuhuan Jiang
Yuhuan Jiang

Reputation: 2726

Append :_* to the parameter in test like this

test(some:_*)

And it should work as you expect.

If you wonder what that magical :_* does, please refer to this question.

Upvotes: 155

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