Question

Working on someone else’s code. Came across a piece of code while analyzing the project

self.groupPicker = [[UIPickerView alloc] initWithFrame:CGRectMake(0,260,320,216)];
self.groupPicker.delegate = self;
self.groupPicker.showsSelectionIndicator = YES;
[self.view addSubview:self.groupPicker];

Where groupPicker is a UIPicker property. When analyzing the project I encountered a potential leak warning in this case. I have also noticed that the groupPicker property is not being released in the dealloc method. Nor is _groupPicker released anywhere in the project. What should be done in this case?

1. Should I remove the UIPicker property and just declare a UIPicker variable instead.

2. Should I just release groupPicker like [_groupPicker release];

What would be the retain count of groupPicker as it is retained once in the .h file and again being allocated as shown in the above piece of code.

Answer 1

1) No, it is perfectly fine to have the property, the problem is that it is being over retained. When you alloc/init the retain count is 1, then you use the retained property which increases the retain count again. The retain count is now 2 and assuming you release the object in dealloc, you end up with a retain count of 1, i.e. a leaked object.

There are many ways you can handle the problem. I think the best way is to autorelease the object on initialization. Like so

self.groupPicker = [[[UIPickerView alloc] initWithFrame:CGRectMake(0,260,320,216)] autorelease];

2) Anything you retain should be released in dealloc, so in dealloc you should

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