What (()?) and ()? means in swift?

Question

var aa: (()?) = (john.residence?.address = someAddress)
var bb: ()? = john.residence?.printNumberOfRooms()

Is this to distinguish whether only nil?

Answer 1

() is the empty tuple type (same as Void).

()? is the optional version of that.

(()?) is a tuple containing the type ()? so reduces to just ()?