Is vararg in kotlin useless?

Question

I am thinking about vararg (variable arguments) option in kotlin. I know it was here before kotlin in time of java, but I actually never really understand benefit of using it. If i want for example for my function myFun() to take variable number of arguments (let's say Strings), I would create myFun() in a way that it takes List of Strings. I don't see any reason for using vararg.

Is there any benefit of using vararg over List, am I missing something?

Answer 1

vararg gives you freedom to call a function with infinite number of arguments without wrapping them in a collection. Using argument of List type, you are in control of more than just arguments, such as mutability.

This is more opinioned answer.

Answer 2

You are right, passing a list is one option to avoid vararg.

For you as the implementor of the function there is no real difference, but for the consumer it is. It's a question of function design. How do you want your clients to call your functions.

Passing a list forces the caller to create a list first and populate it with all the items before passing them to the function.

fun foo(list: List<Int>) { ... }

val list: List<Int> = listOf(1,2,3,4,5)
foo(list)

If you offer a function taking a vararg type the way how to call that function changes.

fun bar(vararg items: Int) { ... }

fun bar(1) // just passing one parameter
fun bar(1,2,3) // or maybe three, etc.

Both ways have their usecases.