Zombie UIWebView when it's deallocated just after alert() called from javascript - ios

Question

I'm using a UIWebView, and it pops an alert when a button is clicked(from javascript). There is another button (in native side), which closes controller, so deallocs also UIWebView.
The problem is, if I touch the button in UIWebView, and touch to close button before alert is populated, my controller and UIWebView are deallocated, but alert remains on screen. Then if I click any button on alert, application crashes and gives following error:
[UIWebView modalView:didDismissWithButtonIndex:]: message sent to deallocated instance
And this method is called from private method
[UIModalView(Private) _popoutAnimationDidStop:finished:]
I'm using ARC, and my dealloc is like this:
- (void)dealloc {
[_myWebView stopLoading];
_myWebView.delegate = nil;
_myWebView = nil;
}
But this does not solve my problem because I think UIModalView has a reference of my webview as a delegate, and I could not set it to nil because its private.
How can I solve it?
Regards

Answer 1

Find a way to set the delegate on UIAlertView to nil before deallocating UIWebView.

Answer 2

This is an Apple bug in their handling of the alert view. Open a bug report.
In the meantime, here are some workarounds:
Create a category on UIAlertView:
#interface UIAlertView (QuickDismiss) #end
#implementation UIAlertView (QuickDismiss)
- (void)__quickDismiss
{
[self dismissWithClickedButtonIndex:self.cancelButtonIndex animated:NO];
}
#end
Now, in your view controller's dealloc method, call this:
[[UIApplication sharedApplication] sendAction:#selector(__quickDismiss) to:nil from:nil forEvent:nil];
This will dismiss all alert views that are currently open, including the ones displayed by your web view.
If that does not work, you can always iterate all subviews of all UIApplication.sharedApplication.windows objects, checking whether [view.class.description hasPrefix:#"UIAlertView"] is true, and dismissing that. This is a less elegant method than the previous one, and should be last resort.
Good luck.

Answer 3

Finally, I find a great solution which actully works. I use method swizzle to hook UIAlertView Delegate function - (void)didPresentAlertView:(UIAlertView *)alertView
- (void)didPresentAlertView:(UIAlertView *)alertView
{
if ([self.delegate respondsToSelector:#selector(didPresentAlertView:)]) {
[self.delegate didPresentAlertView:alertView];
}
if ([self.delegate isKindOfClass: [UIWebView class]]) {
uiWebView = self.delegate;
}
}
I just retain UIWebView instance in this function so that the UIWebView instance as UIAlertView's delegate will not be released before UIAlertView instance being released.