Why UIAlertView prevents my modal view controller

Question

Let's say that when the user presses a button a message needs to be shown and then a modal view controller is displayed. I would write something like that :

- (void)pickImageButtonPressed:(id)button {

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert"
                                                    message:@"Some alert"
                                                   delegate:nil
                                          cancelButtonTitle:@"OK"
                                          otherButtonTitles:nil];
    [alert show];
    [alert release];

    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    [[UIApplication sharedApplication].keyWindow.rootViewController
     presentModalViewController:picker animated:YES];
    [picker release];
}

With this code, the modal view controller is simply not displayed !

However, if I switch the two blocks of code (show modal first, then show the alert), the view controller is displayed modally and the alert shows up above it, exactly as I want.

My question is: why the alert prevents the modal view controller from being displayed ?

Please note that I do not want to wait for alert to be dismissed before calling presentModalViewController.

---

Update : I figured out that my production code was a bit more complicated than what I first put. I updated the example code and then finally found a simple example to reproduce the problem.

Note that in my production code, the popup is displayed from a place where I don't have any reference to a view controller, that's why I use [UIApplication sharedApplication].keyWindow.rootViewController instead of a direct reference to a view controller

Answer 1

I finally found the answer. The issue really was on this line:

[[UIApplication sharedApplication].keyWindow.rootViewController
 presentModalViewController:picker animated:YES];

When an alert is displayed, [UIApplication sharedApplication].keyWindow.rootViewController is nil !. That's why the picker was never displayed. And that's why it worked when I switched the two blocks.

Now I need to find a way to get the most relevant view controller to present the picker modally...