Display UIAlertController from UIView/NSObject class

My solution is below:

Swift

class alert {
    func msg(message: String, title: String = "")
    {
        let alertView = UIAlertController(title: title, message: message, preferredStyle: .Alert)

        alertView.addAction(UIAlertAction(title: "Done", style: .Default, handler: nil))

        UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(alertView, animated: true, completion: nil)
    }
}

Here is sample usage:

let Alert = alert()
Alert.msg("My alert (without title)")
Alert.msg("This is my alert", title: "Warning!")

I solved an essentially similar problem today. Like Jageen, I ran into a situation where I wanted to present a UIAlertController but from a non-UIViewController class. In my case, I wanted an alert to pop up when the failure block of a HTTP request is run.

This is what I used and unlike our friend here, it worked quite perfectly for me.

UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(errorAlert, animated: true, completion: nil)

The better solution for UIView classes is below

ObjectiveC

UIViewController *currentTopVC = [self currentTopViewController];
currentTopVC.presentViewController......... 

- (UIViewController *)currentTopViewController
{
    UIViewController *topVC = [[[[UIApplication sharedApplication] delegate] window] rootViewController];
    while (topVC.presentedViewController)
    {
        topVC = topVC.presentedViewController;
    }
    return topVC;
}

Swift

var topVC = UIApplication.sharedApplication().keyWindow?.rootViewController
while((topVC!.presentedViewController) != nil){
     topVC = topVC!.presentedViewController
}
topVC?.presentViewController........