Crash on orientation change after calling setViewControllers:animated:

Question

I've been dealing with this (somewhat) random bug for a while and can't figure out the problem. The context: I'm creating an UISplitView iPad app that have a UINavigationController inside the Master view:

Main menu in red, submenu in green and main content in purple.

This UINavigationController does not fill the entire Master view because I need some space to have a vertical menu. When a user select a button on the vertical side menu, it sets something new to the UINavigationController to show a UITableView with options. What I'm doing on every menu selection is:

[self.subMenu setViewControllers:@[subMenuViewController] animated:YES];

What happens is that I don't need to keep the menu history, so what I do is I set a new root view controller to the subMenu every time.

The issue is when I start messing with the device orientation. It doesn't have a clear pattern, but sometimes, when rotating, my app crashes. Now when I run it with Instruments, this is what I get:

167 Zombie      -1  00:32.101.527   UIKit   -[UITableView _spacingForExtraSeparators]

And the interesting thing is that the bad access happens on the previous root view controller of the subMenu. So if I tap "Events" and then after that I tap "Podcasts", the bad access happens on trying to access "EventsViewController".

So I'm guessing something is not right on my way of replacing the root view controller of the subMenu UINavigationController, but I'm not sure what it is. Maybe I need to make sure the current root view controller is released before setting a new one?

Any help is much appreciated. :)

Answer 1

It's not uncommon to crash in system library code due to something you didn't set up quite right. This might be that your UIWindow, UIApplicationMain or its content view or your view controller instance was not retained or got released somehow.

That shouldrotate method won't help if your controller isn't still around.

This is to identify which object got released.

For particularly thorny problems, you could add release, retain, and dealloc methods (that log and call super) to a suspect class of yours and see what's releasing it. Log the -retaincount to keep track (I only use this for diagnostic purposes,)

Or you can try this, set a breakpoint on -[UIDevice setOrientation:] and step through your code in the debugger.

To make debugging easier, you can type call (void)instrumentObjcMessageSends(YES) right in the debugger console to begin logging objc_msgSends to /tmp/, then continue execution and it will trace all the messages that are sent right up until the crash.

Answer 2

So first, you should implement the methods willRotateToInterfaceOrientation, willAnimateToInterfaceOrientation and didRotateToInterfaceOrientation (check the actual signature of these methods) in your view controllers that contain a UITableView.

In each of these methods check the your table view dataSource and delegate. I think this crash is caused by a release of the delegate or table view's datasource.

Also you should check what table view delgate/datasource methods are called during rotation.

And the last thing, make sure you discard the old instances of subMenuViewController and they are properly removed from the parent view controller.