How to declare function type for function with variable number of parameters in Kotlin

Question

I am writing a function that accepts another function and it's arguments, for calling it later. How do I specify the type of function so that it can have any number of arguments?

Looking for something like this.

// this does not compile
fun doLater(func: (vararg) -> Double, args: List<Any>) {
    ...
} 

fun footprintOne(i: int, s: String): Double {...}
fun footprintTwo(cheeses: List<Cheese>): Double {...}

// these should be able to run fine
doLater(::footprintOne, listOf(3, "I love StackOverflow"))
doLater(::footprintTwo, listOf(listOf(blueCheese, bree, havarti)))

Alex G · Accepted Answer · 2022-04-26 20:21:35Z

1

Seems like it isn't possible. vararg parameter in a Kotlin lambda

My best workaround I can suggest is to re-wrap the function into one that takes Array or List for the varargs and take that instead.

answered Apr 26, 2022 at 20:21

Alex G

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Comments

MFazio23 · Accepted Answer · 2022-04-26 20:28:58Z

1

You'll want to use the vararg keyword:

fun doLater(func: (Array<out Any>) -> Double, vararg args: Any) {
    func(args)
}

then you call it like this:

doLater(
    { args ->
        // Function logic
    },
    1, 2, 3
)

https://kotlinlang.org/docs/functions.html#variable-number-of-arguments-varargs

answered Apr 26, 2022 at 20:28

MFazio23

1,32412 silver badges24 bronze badges

1 Comment

Keverly Over a year ago

Oh dear, it seems I didn't write my question clear enough. I'll try to update it

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