Question

I am really new to objc and I am trying to understand as much as possible and get a good routine when it comes to mem management.

My question is if code like this is dangerous (i love short code)

NSMutableArray *items = [[NSMutableArray alloc] init]; 

[items addObject:[[UIBarButtonItem alloc] 
                   initWithTitle:@"Login"
                   style:UIBarButtonItemStyleBordered
                   target:self 
                   action:@selector(tryUserInput)]];

[self.toolbar setItems:items animated:TRUE];
[self.view addSubview:self.toolbar];

[items release];

In the examples I can find people always create the object that they add in the array, add it and then release it. If I alloc it and adds it at the same time, the array will take care of it aye? And I am releasing that when I’m done with it. Also, can I write it like this?

self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc]
initWithTitle:@”Logout”
style:UIBarButtonItemStyleDone
target:nil
action:nil];

Or should I attach an autorelease on that one?

If I understood it correclty, since the “navigationitem” is a property it retains the object and takes care of it. And the array retains all the objects I add to it. So everything should be fine?

Thanks for your help

Answer 1

You need an to send an autorelease to the UIBarButton, or you’ll have a leak.

When you alloc it, it has a “retain count” of +1; when you add it to the array it goes to +2. You need it to go back to +1, so that the only owner will be the array, and the UIBarButton will be deallocated when the array is freed. You can do it in two ways:

[items addObject:[[[UIBarButtonItem alloc] 
               initWithTitle:@"Login"
               style:UIBarButtonItemStyleBordered
               target:self 
               action:@selector(tryUserInput)] autorelease]];

or

UIBarButtonItem *item = [[UIBarButtonItem alloc] 
               initWithTitle:@"Login"
               style:UIBarButtonItemStyleBordered
               target:self 
               action:@selector(tryUserInput)];
[items addObject:item];
[item release];