UIAlertView first deprecated IOS 9

Question

I have tried several ways to use UIAlertController,instead of UIAlertView. I tried several ways but I cannot make the alert action work. Here is my code that works fine in I

Answer 1

I tried the above methods, and no one can show the alert view, only when I put the presentViewController: method in a dispatch_async sentence:

dispatch_async(dispatch_get_main_queue(), ^ { [self presentViewController:alert animated:YES completion:nil]; });

Refer to Alternative to UIAlertView for iOS 9?.