Kotlin. Vararg how to filter null values-CodePudding

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()

CodePudding user response：

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.

CodePudding user response：

Try mapNotNull method

 val notNullArgs = args.mapNotNull { it }

If there will be any null it it will be filtered

CodePudding user response：

Your apiMethod() should fail either filter out nulls or just fail if provided list that contains null

fun apiMethod(a : Int, b : String, vararg params : List<Any?>){
   require(params.size == params.mapNotNull { it }.size) {
        "Params must not contain null values"
   }
   // or 
   val filtered = params.mapNotNull { it } 
  
}