didReceiveMemoryWarning Crash

Question

-Using ARC

-I have 5 separate view controllers all subclassing a class I made called "UIViewControllerWithLoadingView" which subclasses UIViewController.

-In both the subclasses and superclass I allocate and deallocate properties like this:

@property (strong, nonatomic) NSURLConnection *urlConnection;

- (void)viewDidUnload
{
    [super viewDidUnload];
    self.urlConnection=nil;
}

-Now when didReceiveMemoryWarning is called, the sub classes viewDidUnload method acts fine. BBBUUTTT if I set properties to nil in the super class, UIViewControllerWithLoadingView, the application will crash. Particularly right where I set the properties of the sub class to nil. So for right now I just don't set the properties to nil in the superclass, which becomes problematic because the live bytes just keep piling up at run time.

What is the exception you get on a crash? (If it doesn't tell you already, use @try/@catch to find out.) — Phillip Mills, Jul 23 '12 at 12:26
"Thread 1: EXC_BAD_ACCESS (code=2,address=0x8)" I'm unable to get the description of the exception because the app crashes before I can log it — MobileMon, Jul 23 '12 at 12:41
Set a breakpoint on Objective-C exceptions using the Breakpoint navigator **or** put the @try/@catch around the first line of the program (in main.m). — Phillip Mills, Jul 23 '12 at 12:46
Still won't print the exception...tried in both simulator and physical device. The app just crashes before printing — MobileMon, Jul 23 '12 at 14:33
I don't think this exception can be raised by NSException. Certain exceptions can't be caught, objective c doesn't work like Java where it catches anything — MobileMon, Jul 23 '12 at 18:18
I believe that if it's an exception that's thrown after the app starts to execute `main` it can be caught. Sometimes apps are killed by signals, however, and sometimes they fail during launch. Those are tough to diagnose. — Phillip Mills, Jul 23 '12 at 18:29

score 0 · Answer 1 · answered Jul 23 '12 at 14:00

0

The rule of thumb is that methods that "clean up"--like dealloc or viewDidUnload--should make the call to super after they do everything else. (And methods that "set up"--like init--call to super first.) I can't tell if that's your problem without seeing all your subclass implementations, but that would be a place to start.

answered Jul 23 '12 at 14:00

Husker Jeff

857
1
5
6

Although I did have some super calls in the wrong place according to your comments, this still did not fix the problem – MobileMon Jul 23 '12 at 14:33

score 0 · Accepted Answer · answered Jul 24 '12 at 14:07

The problem was in the superclass I had a view that extended uiview which had a property reference to the viewcontroller. Well dealloc is automatically called in arc so dealloc would actually set the viewcontroller itself to nil causing a crash. Once I removed the property of the viewcontroller in the custom view class the problem no longer occurred

didReceiveMemoryWarning Crash

2 Answers2