Show UIAlertController if already showing an Alert

Question

Difference between the legacy UIAlertView and the new UIAlertController is that the latter needs to be presented onto a specific viewcontroller with presentViewController:animated:completion:. This poses an awkward problem for my use case: what if there is already an UIAlertController showing (e.g. a rating dialog) when a second viewcontroller gets presented (e.g. an error dialog due to failed network connection). I have experienced that in this case the second UIAlertController just does not show.

Edit: At the moment I try to show an alert, I do not know if there currently is anything presenting.

How do you cope with this situation?

Answer 1

I found a workaround to find out which viewcontroller I can present the alert upon. I also posted the answer here:

@implementation UIViewController (visibleViewController)

- (UIViewController *)my_visibleViewController {

    if ([self isKindOfClass:[UINavigationController class]]) {
        // do not use method visibleViewController as the presentedViewController could beingDismissed
        return [[(UINavigationController *)self topViewController] my_visibleViewController];
    }

    if ([self isKindOfClass:[UITabBarController class]]) {
        return [[(UITabBarController *)self selectedViewController] my_visibleViewController];
    }

    if (self.presentedViewController == nil || self.presentedViewController.isBeingDismissed) {
        return self;
    }

    return [self.presentedViewController my_visibleViewController];
}

@end

// To show a UIAlertController, present on the following viewcontroller:
UIViewController *visibleViewController = [[UIApplication sharedApplication].delegate.window.rootViewController my_visibleViewController];

Answer 2

Since UIAlertController is itself a UIViewController, you can present a second UIAlertController on top of the first one by presenting from the existing one:

alertController.PresentViewController(alertController2,  animated: true, completionHandler: null)