Error when show Alert

[iThanh]

Hello developer and everybody,

When I try to show alert, I receive this error:

fatal error: unexpectedly found nil while unwrapping an Optional value

In line: let rv = UIApplication.shared.keyWindow! as UIWindow

Help me, please!

[lucasbordini]

same here

[soypaduano]

same

[DetectorApps]

Hi guys, In my case, i am having that problem because i showed the alert in viewDidLoad method of the controller. I moved it to viewDidAppear and the alert started to work well.