Repeated TableViewCells show up when I try to reuse tableviewcells... how do I get the new ones to show?

Question

I am having a problem with my code skipping over the if(cell == nil) after about nine trips through the cellForRowAtIndexPath. Then items in my table start repeating and do so every nine items. When I remove the if(cell == nil) line, the table comes out beautifully, with all the data in the right order. However, if I scroll to the bottom of the table, my app crashes so that is not a good solution. Any ideas please??

Thank you!

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];


    if (cell == nil) {

        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier] autorelease];     


    NSString *temp = [[views objectAtIndex:indexPath.row] objectForKey:@"racer"];
    NSString *val = [[views objectAtIndex:indexPath.row] objectForKey:@"pointsScored"];

    // Set up the cell...
    cell.textLabel.text = temp;
    cell.textLabel.font = [UIFont boldSystemFontOfSize:15];
    cell.detailTextLabel.text = val;

    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

    [temp release];
    [val release];

    }

    return cell;
}

Answer 1

KLevSki,

That is because you are re-using tableview cells via dequeueReusableCellWithIdentifier which is a good thing on the iPhone platform. What happens is this:

1) Cell is created in the if (cell==nil) section

2) Once a number of cells are created (in your case 9 of them, based roughly on how many are shown on screen), the OS begins to re-use the table cells to be a good memory manager instead of creating a unique table cell for each and every row which could be memory intensive

3) Since the cell is being re-used, all you need to do in the section after the if (cell==nil) block is to update/change the information on each cell.

As an example... If you created a cell that had only an icon and a label on it, each time the cell is scrolled into view, you would update the icon and label to whatever image/string is appropriate for that cell.

For your case:

...

if (cell == nil) {

    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier] autorelease];     

    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

}

// update cell
cell.textLabel.text = [[views objectAtIndex:indexPath.row] objectForKey:@"racer"];
cell.textLabel.font = [UIFont boldSystemFontOfSize:15];
cell.detailTextLabel.text = [[views objectAtIndex:indexPath.row] objectForKey:@"pointsScored"];

return cell;