In iOS 11, dismissing a modally presented navigation controller results in visual duplication

Question

I have a modally presented UINavigationController. Onto that navigation controller, two view controllers are pushed. The whole modal presentation should be dismissed from the second view controller upon pressing a Done button. To do this, dismiss is called on the presentingViewController:

@IBAction func doneWasPressed(_ sender: UIBarButtonItem) {
    presentingViewController!.dismiss(animated: true)
}

In iOS 11, when an ancestor within the navigation controller has presented a UISearchController, which is added to the navigationItem, dismissing the navigation controller causes a visual artefact whereby a duplicate of the view is visible underneath the animating view. Once the top view has moved out of view, the duplicate underneath suddenly disappears. See the gif below for a screen recording of the issue.

A small reproducible example is available in this GitHub repository. It was created on Xcode 9 (GM) using Swift 4.

Is there a known workaround?

---

Answer 1

In preparing your minimal, complete, and verifiable example, you noticed that the problem was the presence of the UISearchController. I noticed that even after I pushed to the second page view controller (past the view controller with the UISearchController), that the search controller was still there:

If you set the isActive to false when the view disappears, this problem goes away.

override func viewDidLoad() {
    super.viewDidLoad()

    let searchController = UISearchController(searchResultsController: nil)
    searchController.obscuresBackgroundDuringPresentation = false
    searchController.hidesNavigationBarDuringPresentation = false
    navigationItem.searchController = searchController
    navigationItem.hidesSearchBarWhenScrolling = false
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)

    navigationItem.searchController?.isActive = false
}

And, when this is done, the dismissal works as expected.

---

My original answer, suggesting that you want to dismiss the navigation controller, not the presenting view controller, is below.

---

If you presented the navigation controller modally, and then pushed a few view controllers from there, you don't want to dismiss the presentingViewController, but rather the navigationController, e.g.:

navigationController?.dismiss(animated: true)

Or, alternatively, create an unwind action on your view controller to which you want to return:

@IBAction func unwindHome(_ segue: UIStoryboardSegue) {
    // this is intentionally blank
}

Then you can create an unwind segue right in IB:

Or if you have to do it programmatically, create an unwind segue between the view controller and the "exit" outlet, and then you can performSegue(withIdentifier:sender:).