ios - "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?

question from:https://stackoverflow.com/questions/39559212/oldvalue-and-newvalue-default-parameters-names-inside-willset-didset-unrec

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)")
    }
}