Kotlin: Can you use named arguments for varargs?

Question

For example, you might have function with a complicated signature and varargs:

fun complicated(easy: Boolean = false, hard: Boolean = true, vararg numbers: Int) 

It would make sense that you should be able to call this function like so:

complicated(numbers = 1, 2, 3, 4, 5) 

Unfortunately the compiler doesn't allow this.

Is it possible to use named arguments for varargs? Are there any clever workarounds?

Answer 1

To pass a named argument to a vararg parameter, use the spread operator:

complicated(numbers = *intArrayOf(1, 2, 3, 4, 5)) 

Answer 2

It can be worked around by moving optional arguments after the vararg:

fun complicated(vararg numbers: Int, easy: Boolean = false, hard: Boolean = true) = {} 

Then it can be called like this:

complicated(1, 2, 3, 4, 5) complicated(1, 2, 3, hard = true) complicated(1, easy = true) 

Note that trailing optional params need to be always passed with name. This won't compile:

complicated(1, 2, 3, 4, true, true) // compile error 

Another option is to spare vararg sugar for explicit array param:

fun complicated(easy: Boolean = false, hard: Boolean = true, numbers: IntArray) = {}  complicated(numbers = intArrayOf(1, 2, 3, 4, 5))