Hi all, I want to define a kotlin function as a parameter for a class and I want that kotlin functio...

# announcements

[Lauren Yew]

Hi all, I want to define a kotlin function as a parameter for a class and I want that kotlin function to be able to have 0 or more arguments. Is there a way to do that?
Ex:

class Builder (
private val function: (suspend () -> String) //Don't want to force Builder to have to provide a no argument function
)

Context: I used to be able to do this in RxJava with a Single. Moving to Coroutines / Flow.

[Vampire]

How will you call function if you don't know how many arguments it will have?

[Lauren Yew]

good point, but we use vararg in other functions...

[Lauren Yew]

Good point. What I guess I really want is to provide a function (with no args)

[Lauren Yew]

and be able to pass a function that took in args?

[Lauren Yew]

Ex:

val builder = Builder(::exampleFunc)
func exampleFunc(x: Int): String {...}

[Vampire]

Same question with that example, who will provide the argument given to x?

[Vampire]

Surely not the builder, as it should not even know how many arguments are there, let alone give arguments for them

[Lauren Yew]

caller of builder?

[Vampire]

At what place?

[Lauren Yew]

Yeah builder doesn't care on number of arguments, it just wants to invoke the suspend function and get a result

[Vampire]

So maybe you mean like that:

class Builder(
        private val function: suspend () -> String
)

fun exampleFunc(x: Int): String = ""
val builder = Builder { exampleFunc(1) }

[Vampire]

You give it a function that calls your function with the parameters you want

[Lauren Yew]

oh ok thank you!

[Vampire]

yw

[Youssef Shoaib [MOD]]

If you will always make sure that only the caller of builder calls the method, then you can do something like this:

class Builder<R, T: KFunction<R>>(private val func: T) {
    inline fun callFunction(caller: T.() -> R) = func.caller()
}