Kotlin null check for multiple nullable var's

Language Design
51

I also tried to find a generic solution for this. I ended with following code:

fun <T : Any> allNotNull(vararg elements: T?): List<T>? = if(elements.contains(null)) null else elements.filterNotNull()

I can now write something like

val firstName = parameters["firstName"]
val lastName = parameters["lastName"]

 allNotNull(firstName, lastName)?.apply {
     userService.add(UserDTO(firstName = this[0], lastName = this[1]))
 }

The UserDTO needs String parameters, but parameters[“firstName”] is of type String? . I don’t like the syntax with this[0] much, but it is still better as chaining multiple let-calls.