Is a ViewController unloaded from memory after being dismissed?

Question

I noticed that the state of variables doesn't preserve among different presentations of a View Controller.

    var starrySky = StarrySky() // this has a state property which is false initially
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        if starrySky.state == false { starrySky.createSky(for: self.view) }
        if starrySky.state != false { starrySky.resumeSkyAnimations()} // this never runs

    }
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        starrySky.state = true // here im changing the state
        starrySky.removeSkyAnimations()
    }

So whenever I dismiss this ViewController and present it again my starrySky.state is always false. I have the same code in the same methods in my rootViewController and whenever I change views the state preserves.

• So does this mean that any VC's presented modally are dismissed from memory after you call dismiss(animated:,completion:) ?

Answer 1

So does this mean that any VC's presented modally are dismissed from memory after you call dismiss

Normally, yes. View controllers form a hierarchy or chain of parent/presenter and child/presented. The former owns and retains the latter, and releases it when the latter is removed. The root controller is never removed unless you deliberately replace it.

Answer 2

Because when you present the view again the variable starrySky is initialized again with false you can save the state using userDefaults in viewWillDisappear and read it in viewWillAppear