NSZombieEnabled prevents my app from crashing

Question

So I've been debugging like a mad men using NSZombiesEnabled and NSZombies in Instruments. However when running the app using zombies it seems to resolve my issue. When I run the app without NSZombiesEnabled or NSZombies in instruments it crashes. Any idea on how to deal with this?

So the issue is that I am releasing something twice, but can't seem to find where I am doing this. Turning on NSZombieEnabled won't help as the program runs fine without telling me where I am over releasing.

So I think I kind of know where it's crashing, I have this globalArray Singleton class that I am creating:

extern NSString * const kClearDataSource;

@interface AHImageDataSource : NSObject
+ (AHImageDataSource *)sharedDataSource;
- (void) clearDataSource;
- (void) addObject:(id) object;
- (void) addObject:(id)object atIndex:(int) index;
- (int) count;
- (id) objectAtIndex:(int) index;
@end



NSString * const kClearDataSource = @"clearDataSource";

@interface AHImageDataSource()
{
    NSMutableArray * imageDataSource_;
}

@property (nonatomic, retain) NSMutableArray * imageDataSource_;

@end

@implementation AHImageDataSource
@synthesize imageDataSource_;

+ (AHImageDataSource *)sharedDataSource {
    static AHImageDataSource *_sharedClient = nil;
    static dispatch_once_t oncePredicate;
    dispatch_once(&oncePredicate, ^{
        _sharedClient = [[self alloc] init];
    });

    return _sharedClient;
}


- (id)init {
    self = [super init];
    if (!self) {
        return nil;
    }

    NSMutableArray * temp = [[NSMutableArray alloc] initWithCapacity:200];
    self.imageDataSource_  = temp;
    [temp release];


    return self;
}

-(void) clearDataSource
{
    if ([self.imageDataSource_ count] > 0){
        [self.imageDataSource_ removeAllObjects];
    }
}

- (void) addObject:(id) object
{
    [self.imageDataSource_ addObject:object];
}

- (void) addObject:(id)object atIndex:(int) index
{
    [self.imageDataSource_ insertObject:object atIndex:index];
}

- (int) count
{
    return [self.imageDataSource_ count];
}

- (id) objectAtIndex:(int) index
{
    if (index >= 0 && index < [self.imageDataSource_ count]){
        return [self.imageDataSource_ objectAtIndex:index];
    } 

    return nil;
}

- (void) dealloc
{
    [super dealloc];
    [imageDataSource_ release];
}

@end

at one point of the code I am trying to remove all of the objects in the array and then adding some stuff in. When that happen the crashed happened.

This part of the code crashes the second time it was executed:

 NSArray *arr = [response valueForKey:@"data"];
                 if ([arr count] > 0){
                     [[AHImageDataSource sharedDataSource] clearDataSource];
                 }

                for (NSDictionary * data in arr){
                     AHInstagramImageData * imgData = [[AHInstagramImageData alloc] initWithData:data];
                     [[AHImageDataSource sharedDataSource] addObject:imgData];
                     [imgData release];
                 }

check this [http://stackoverflow.com/questions/4164233/nszombieenabled-fixes-my-app](http://stackoverflow.com/questions/4164233/nszombieenabled-fixes-my-app) — Malek_Jundi, May 21 '12 at 21:36

score 3 · Accepted Answer · answered May 22 '12 at 00:16

3

You should definitely not do [super dealloc] first in your -dealloc method. It must come last.

answered May 22 '12 at 00:16

Ken Thomases

88,520
7
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Also, you should use ARC, in which case, you don't need the [super dealloc] statement at all. – Keller Sep 13 '12 at 20:42
Having [super dealloc] first is what caused the issue for me. – Daniel G. Wilson Feb 14 '13 at 17:52

score 1 · Answer 2 · answered May 21 '12 at 21:27

1

Go go Product -> Analyze. The messages displayed will give you the solution or an idea.

answered May 21 '12 at 21:27

Teofilo Israel Vizcaino Rodrig

1,480
1
13
25

score 1 · Answer 3 · answered May 21 '12 at 21:36

1

Your app crashes when an object that has been deallocated is sent a message. NSZombiesEnabled prevents your app from crashing because it holds on to all deallocated objects (and thus leaks everything). It will print a message in the console when a deallocated object is sent a message (which would normally crash your app). Something to the affect of "message 'bar' sent to deallocated object 'foo'" (or something like that). It does not actually pause execution of your app.

When you've passed the point where you know your app generally crashes, check the console log for a message similar to the one above.

answered May 21 '12 at 21:36

sc0rp10n

1,118
7
8

so you'r saying to turn on NSZombiesEnabled? – adit May 21 '12 at 21:41
Yes, for troubleshooting your code, you can turn it on and then when the app doesn't crash where it normally does, look in the console to see what message is sent to a deallocated object. – sc0rp10n May 21 '12 at 21:54
2

nothing is outputted to the console when NSZombieEnabled is there – adit May 21 '12 at 22:05
As I recall, the Zombies instrument *does* automatically stop your app when a deallocated instance is messages. – Ken Thomases May 22 '12 at 00:18

NSZombieEnabled prevents my app from crashing

3 Answers3