Why is object not dealloc'ed when using ARC + NSZombieEnabled

Question

I converted my app to ARC and noticed that an object alloc\'ed in one of my view controllers was not being dealloc\'ed when that view controller was dealloc\'ed. It took a w

Answer 1

This is a bug that has been acknowledged by Apple in Technical Q&A QA1758.

You can workaround on iOS 5 and OS X 10.7 by compiling this code into your app:

#import 

@implementation NSObject (ARCZombie)

+ (void) load
{
    const char *NSZombieEnabled = getenv("NSZombieEnabled");
    if (NSZombieEnabled && tolower(NSZombieEnabled[0]) == 'y')
    {
        Method dealloc = class_getInstanceMethod(self, @selector(dealloc));
        Method arczombie_dealloc = class_getInstanceMethod(self, @selector(arczombie_dealloc));
        method_exchangeImplementations(dealloc, arczombie_dealloc);
    }
}

- (void) arczombie_dealloc
{
    Class aliveClass = object_getClass(self);
    [self arczombie_dealloc];
    Class zombieClass = object_getClass(self);

    object_setClass(self, aliveClass);
    objc_destructInstance(self);
    object_setClass(self, zombieClass);
}

@end

You will find more information about this workaround in my blog post Debugging with ARC and Zombies enabled.