Xcode应用程序在Iphone上运行但在Ipad上崩溃

Question

I made a universal application that contains NIB files for both ipad and iphone UI's. In my view controllers initWithNibName method I call UIUserInterfaceIdiomPad == UI_USER_INTERFACE_IDIOM() to detect whether the controller is running on iphone or ipad.

I then launch their respective nib files. When I run the app on iphone, it works fine, but when I run it on ipad it eventually crashes with a EXC_BAD_ACCESS error. This error occurs when I use a view controller to launch another view controller, which then launches another one in the navigation stack. This error occurs as soon as I click the view that belongs to the third controller of the stack.

I cannot distinguish a difference between the NIB files that would cause a crash. I have been working tirelessly to figure out why this is happening but I cannot fix this error. Does anyone have any insight into what might be going on?

Any advice on how to approach fixing this problem would be very appreciated.

Answer 1

The first thing you should do is enable the "All Exceptions" break point. This will often accurately tell you the line of code where the EXC_BAD_ACCESS is happening.

Next, I would turn on zombies and see where the over-release is happening. To do so, in Xcode, while holding the option key, click Product | Run.... In the ensuing window, add NSZombieEnabled to the environment variables list.

Then run. Do the normal things you do to cause the crash and see where the debugger lands. With any luck, it will stop where the problem is actually occurring.

When you get a EXC_BAD_ACCESS it means you're trying to access/release something that's already been released. If you're in a non-ARC situation, it normally means you've inadvertently released something when you didn't mean to, so just check for alloc/init and release balance. If, however, you're in an ARC situation, I would bet it has to do with not niling a delegate when a view controller gets released.

For example, if you have a MKMapView and have set its delegate to your view controller, you should nil its delegate when your view gets unloaded or dealloc'd. Otherwise, messages will continue to get set to it. Or, another possibility is that you've added your view controller as an NSNotificationCenter observer and didn't remove it as an observer when the view controller was unloaded or dealloc'd.

Another possibility is that you're re-using view controllers between the two versions of your universal app. If you are accessing anything by an identifier that doesn't exist in the nib for the iPad, that would cause a crash--though if you're using nibs as opposed to storyboards, that may not be an issue.

That's about all I can think of for now. Try to zero in on where it's happening and post code here if you still can't figure it out.

Best regards.