Question

I just added some code that was taken from the Apple docs which shows how to use custom UITableViewCells that are created from a nib. I’m new to iOS development, so I’m still learning about proper memory management and the code isn’t exactly clear to me as to how it works in the first place. When I run the Allocations instrument, it shows unallocated memory in the code below. Specifically, it shows the UITableViewCells remain alive after the view controller is popped off the nav stack…

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{    
    static NSString *CellIdentifier = @"MyCustomCellIdentifier";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        [[NSBundle mainBundle] loadNibNamed:@"MyCustomCell_iPhone" owner:self options:nil];  //<--Allocations instrument complaining about this line
        cell = customCell;
        [self setCustomCell:nil];
    }

    return cell;
}

customCell is an instance var defined in this view controller, like so…

IBOutlet UITableViewCell *customCell;
@property (nonatomic, retain) IBOutlet UITableViewCell *customCell;

Is there a problem in this code?

Thanks so much for your wisdom!

Answer 1

I compared the code from the documentation:

if (cell == nil) {
    [[NSBundle mainBundle] loadNibNamed:@"TVCell" owner:self options:nil];
    cell = tvCell;
    self.tvCell = nil;
}

With your code:

if (cell == nil) {
    [[NSBundle mainBundle] loadNibNamed:@"MyCustomCell_iPhone" owner:self options:nil];
    cell = [self customCell];
    [self setCustomCell:nil];
}

There seems to be a disparity at the line where you assign cell. Apple’s example code uses tvCell, the instance variable, whereas you use [self customCell], the property getter for the instance variable. Could that be the cause? Try changing

    cell = [self customCell];

to

    cell = customCell;