奇怪的BAD_ACCESS异常iOS

Question

I have a property (noARC)

@property (nonatomic, retain) NSString *itemUUID;

and an initialization

- (void) viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    if (_itemUUID) {
        [self updateViews];
    } else {
       _itemUUID = [[EADataManager sharedInstance] generateUuidString];
        NSLog(@"%@", _itemUUID);
    }
}

The UUID generation method is

- (NSString *)generateUuidString
{
    CFUUIDRef UUID = CFUUIDCreate(kCFAllocatorDefault);
    NSString *uuidString = (NSString *)CFUUIDCreateString(kCFAllocatorDefault, UUID);
    [uuidString autorelease];
    CFRelease(UUID);
    return uuidString;
}

and I try to use this property in a very simple way in another method:

- (IBAction)submitButton:(id)sender
{
    if ([nameField.text length] > 3)
    {
        NSLog(@"%@", _itemUUID);
        NSDictionary *changedData = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:nameField.text, priceField.text, quantityField.text, nil] forKeys:[NSArray arrayWithObjects: @"Name", @"Price", @"Quantity", @"UUID", nil]];
    }
}

So on the second NSLog there is an exception BAD_ACCESS . Can't understand my fault.

Answer 1

Your generateUuidString is returning an autorelease value, so your viewDidAppear should retain it (which you can do by using the setter, self.itemUUID = ... ).

And kambala is correct as well, that you've also added three objects for your four keys of your dictionary.

Answer 2

You forgot to add your UUID to the object list in the dictionary, so number of objects and keys mismatches. Correct dictionary initialization:

NSDictionary *changedData = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:nameField.text, priceField.text, quantityField.text, _itemUUID, nil] forKeys:[NSArray arrayWithObjects: @"Name", @"Price", @"Quantity", @"UUID", nil]];

Answer 3

If you are not using ARC, this

_itemUUID = [[EADataManager sharedInstance] generateUuidString];

is wrong, it assigns an object you do not own to an instance variable. That object will go away when the autorelease pool is drained. Since you have declared a property, you should use it.

[self setItemUUID: [[EADataManager sharedInstance] generateUuidString]];