“oldValue” and “newValue” default parameters names inside willSet / didSet unrecognized

Question

I am currently writing Swift 3 code in Xcode 8.

When using oldValue and newValue default parameters inside the willSet and

Answer 1

You didn't try to initialize the variable with a new object by which you can set your clojure:

var vc:UIViewController? = UIViewController(){
   willSet { 
       print("Old value is \(oldValue)")
   }
   didSet(viewController) {
       print("New value is \(newValue)")
   }
}