Code Quiz

Observer Setup in viewWillAppear

Spot why a notification observer added in viewWillAppear leaks and fires multiple times.

Codeswift

class FeedViewController: UIViewController {

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(refresh),
            name: .dataDidUpdate,
            object: nil
        )
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        // cleanup handled in deinit
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    @objc func refresh() {
        // reload feed data
    }
}

What is the bug in this view controller's lifecycle handling?

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