Kotlin. Vararg how to filter null values

Question

I have an API that has method which takes vararg of some object (fox example Param). I need to filter null params and not put it to vararg. Is it possible ?

I know there is a method in kotlin listOfNotNull but api accepts vararg(

This is example of calling API method (apiMethod(vararg params: Param)):

someFun() {
   apiMethod( 
      Param("first"),
      Param("second"),
      null // need to filter it
    )
}

P.S. I can't change apiMethod()

Answer 1

If I understand your question correctly, you need to filter your arguments before passing them to the function since you cannot modify the function. To do this, you can filter to a List, and then convert that list to a typed array and pass it using the * spread operator:

fun someFun() {
   apiMethod( 
      *listOfNotNull(
          Param("first"),
          Param("second"),
          null // need to filter it
      ).toTypedArray()
    )
}

It's a shame you have to use toTypedArray(). IMO, it should be supported for all Iterables, since Lists are far more common than Arrays. This feature request has not had a lot of attention from JetBrains.