Question

In the following code xCode’s Build & Analyze function detects a

Potential leak of an object allocated on line 165 and stored into ‘addButton’.

addButton is a UIBarButtonItem using the category barItemWithImage (which I read about here) which returns an autoreleased object. If I don’t retain addButtonItem I get an exception on trying to access a released object.

What am I missing here?

        UIBarButtonItem *addButton;

    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        addButton = [UIBarButtonItem barItemWithImage:[UIImage imageNamed:@"RedPlus.png"] target:self action:@selector(createStoryModal:)];
    }else {
        addButton = [UIBarButtonItem barItemWithImage:[UIImage imageNamed:@"RedPlusiPhone.png"] target:self action:@selector(createStoryModal:)];
    }

    [addButton retain];

    NSArray* toolbarItems = [NSArray arrayWithObjects:
                             addButton,
                             [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace 
                                                                           target:nil
                                                                           action:nil],
                             nil];

    [toolbarItems makeObjectsPerformSelector:@selector(release)];
    self.toolbarItems = toolbarItems;

The category code:

    @implementation UIBarButtonItem(MyCategory)

+ (UIBarButtonItem*)barItemWithImage:(UIImage*)image target:(id)target action:(SEL)action{
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button setImage:image forState:UIControlStateNormal];
    [button setFrame:CGRectMake(0.0, 0.0, image.size.width, image.size.height)];
    [button addTarget:target action:action forControlEvents:UIControlEventTouchUpInside];

    return [[[UIBarButtonItem alloc] initWithCustomView:button] autorelease];
}

@end

Answer 1

the static analyzer is right.

remove this:

[addButton retain];

and this:

[toolbarItems makeObjectsPerformSelector:@selector(release)];

and you’re also leaking a UIBarButtonItem.

NSArray retains its elements.

There may be other memory issues elsewhere, but that should remove three of the visible issues/bad forms.