Question

UPDATE:

Seems to me like it is pretty much an Apple bug. I tried the following:

1. create a new single-window project
2. create a single UIPickerView like the one shown below, only that the
   picker just allows for turning the dials. That is, neither variables
   nor any state is manipulated when interacting the picker.

RESULT: No matter whether I use the simple titleForRow:forComponent or viewForRow:forComponent, the picker still leaks 48 bytes each time a dial is turned. Further, I even tried having the picker return views previously allocated in an array set up as a class property in the viewController, so that no views are retained or released but for whatever the picker might do internally after or before it calls the delegate methods. And still, the leaks occur.

Seems like an Apple bug to me.

ORIGINAL QUESTION

I have a textField whose imputView is set to a UIPickerView with 4 components. The picker is used to select a weight / mass which becomes the text in the textField.

Under Instruments, each time I turn a dial / component in the UIPickerView, a leak occurs:

Here’s the stack trace for the 48 byte leak:

The code through which the UIPickerView gets each component view is:

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view
{
    if(!view)
    {
        view = [[[UILabel alloc] initWithFrame:CGRectMake(0, 0, 0, 37)] autorelease];
        UILabel *label = (UILabel*)view;
        label.autoresizingMask = UIViewAutoresizingFlexibleWidth;
        label.textAlignment = UITextAlignmentCenter;
        label.font = [UIFont boldSystemFontOfSize:24];
        label.backgroundColor = [UIColor clearColor];
    }

    ((UILabel*)view).text = [NSString stringWithFormat:@"%@%i", ((component == 3) ? @"." : @""), row];
    return view;
}

- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component
{
    return  60;
}

And the code that updates the textField to the new textual value is:

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    NSString *newWeight = [NSString stringWithFormat:@"%i%i%i.%i", 
                           [pickerView selectedRowInComponent:0], 
                           [pickerView selectedRowInComponent:1],
                           [pickerView selectedRowInComponent:2],
                           [pickerView selectedRowInComponent:3]];

    self.sampleMassBuffer = [NSDecimalNumber decimalNumberWithString:newWeight];
    weightTextField.text = [[numberFormatter stringFromNumber:self.sampleMassBuffer] stringByAppendingFormat:@" %@", currentConfiguration.weightUnits];
}

I have no idea how the leaks are originating or if they are even mine!
Could it be an Apple bug?

Answer 1

The leak in the SDK. I just confirmed with a trusted source.