child

gistfile1.txt

class SuperClass {
  public var customInt: Int? {
    didSet {
      print("super")
    }
  }
}

class ChildClass: SuperClass {
  override public var customInt: Int? {
    didSet {
      print("child")
    }
  }
}

var obj: ChildClass
obj = ChildClass()
obj.customInt = 4