Why my alert is not in the view hierarchy

Question

I found that my controller is out of the view hierarchy in this code andI call this in viewDidLoad:

if CLLocationManager.locationServicesEnabled() {
    // code
} else {
    let alertController = UIAlertController(...)
    //
    present(alertController)
}

If I wrap else clause in .async or .asyncAfter in the main queue I have my issue go away. Why do this happen here?

Thank you!

i think you called UIAlertController in viewdidload , try in viewdidappear — Anbu.Karthik, Feb 15 '19 at 07:49
This method called in viewDidLoad! Here is the issue I suppose? — wm.p1us, Feb 15 '19 at 07:50
yes ,see the difference between viewdidload or viewdidappear : https://stackoverflow.com/questions/11254697/difference-between-viewdidload-and-viewdidappear — Anbu.Karthik, Feb 15 '19 at 07:52
@Anbu.Karthik I got it. View is not in the hierarchy when alert appeared. My bad! — wm.p1us, Feb 15 '19 at 07:55

Anbu.Karthik · Accepted Answer · 2019-02-15T08:09:53.320

1

based on your question you are tried to load UIAlertController before load the UIviewcontroller hierarchy, in here you can do it two ways,

you can forcefully load the UIAlertController in the main thread, so in here you need to use .async or .asyncAfter, but it's not suggested.
alternate suggestion but it will works fine, you need to wait for your initial UI view hierarchy, I mean you need to convert your code from viewDidLoad to viewDidAppear. for ref : Difference between viewDidLoad and viewDidAppear

edited Feb 15 '19 at 08:09

answered Feb 15 '19 at 08:05

Anbu.Karthik

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"load the UIAlertController in the main thread". What does that even mean? You cannot use `viewWillAppear. You have to use `viewDidAppear` because otherwise `self` is not in the view hierarchy yet and there is no way to present a controller outside the view hierarchy. – Sulthan Feb 15 '19 at 08:08

Why my alert is not in the view hierarchy

1 Answers1