Navigation bar buttons set during viewDidLoad don't appear until after view has appeared in iOS 11 - ios

Question

In iOS 10, I could determine the list of navigation bar buttons I want to appear in viewDidLoad, and they would appear in the navigation bar as the view controller transitioned in.
In iOS 11, I can no longer do this. Whatever navigation bar buttons were set in interface builder are displayed as the view controller transitions in, and my custom list of buttons are not displayed until after the view finishes sliding in. Updating the buttons in viewWillAppear does not help.
Is this simply a bug in iOS 11, or is there something else I should be doing? Is there a workaround so I can continue to display buttons while the screen loads?
In the following example, I have set a button "Default Button" in the storyboard, and override it with an "Edit" button in viewDidLoad. The project is available on Github.
iOS 10
iOS 11

Answer 1

It looks like the issue is that navigation bar icons displayed during the transition appear to be fixed when the view controller is passed off to the navigation controller. By the time that viewDidLoad is called, the icons have already been fixed.
In order to fix this, we need to update the navigation bar icons on the view controller's navigationItem before the view controller is pushed onto the navigation controller stack.
One way to do this would be to setup the navigation bar icons in awakeFromNib. This is what #Joe's answer was effectively doing, because apparently viewDidLoad is called from awakeFromNib when isViewLoaded is true during awakeFromNib.
However, doing this in awakeFromNib prevents you from taking into account any properties set on the view controller in prepareForSegue. So another option (and the one that I am using) is to force the entire view to load in prepareForSegue by adding the line _ = controller.view after setting any desired properties.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "showDetail" {
if let indexPath = tableView.indexPathForSelectedRow {
let controller = (segue.destination as! UINavigationController).topViewController as! DetailViewController
...
_ = controller.view
}
}
}

Answer 2

Move your Edit barButton code from viewDidLoad to isViewLoaded method as below.
override var isViewLoaded: Bool {
self.navigationItem.rightBarButtonItem = self.editButtonItem
return true
}
Output:
Note: Above code will fix the transition delay issue. Really, don't have much to explain why this happening. I experienced similar issue in iOS 10 as well NavigationBar delay updating barTintColor iOS10. It could be another bug in iOS11.
PS:
After reading Apple Doc about isViewLoaded and comparing other view loading methods. Its all about loading memory upon view loads.
You don't really need to move you barButton code at all.Just implement the isViewLoaded method and return to true as below:
override var isViewLoaded: Bool { return true}