"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 didSet blocks, I am getting "unresolved identifier" compiler error.

I have a very basic code as below

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

Apple Documentation for Swift 3 still seems to support these feature. I hope I am not missing anything here?

Answer 1

You can also use vc:

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