Accessory view in UITableView: view doesn't update

Question

I'm trying to add checkmarks to items when the user select rows in a table view. However, the view is not refreshed and the checkmarks do no show up:

- (void)tableView:(UITableView *)tv didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    UITableViewCell* oldCell = [self tableView:tv cellForRowAtIndexPath:[NSIndexPath indexPathForRow:selectedIndex inSection:0]];
    oldCell.accessoryType = UITableViewCellAccessoryNone;

    if (indexPath.section == 0) {
        selectedIndex = indexPath.row;
    }

    UITableViewCell* newCell = [self tableView:tv cellForRowAtIndexPath:indexPath];
    newCell.accessoryType = UITableViewCellAccessoryCheckmark;

    [tv deselectRowAtIndexPath:indexPath animated:NO];
}

What could be a reason for that?

Answer 1

Call cellForRowAtIndexPath directly on the tv object instead of through self to make sure you get a proper cell reference back:

- (void)tableView:(UITableView *)tv didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    UITableViewCell *oldCell = [tv cellForRowAtIndexPath:[NSIndexPath indexPathForRow:selectedIndex inSection:0]];
    oldCell.accessoryType = UITableViewCellAccessoryNone;

    if (indexPath.section == 0) {
        selectedIndex = indexPath.row;
    }

    UITableViewCell *newCell = [tv cellForRowAtIndexPath:indexPath];
    newCell.accessoryType = UITableViewCellAccessoryCheckmark;

    [tv deselectRowAtIndexPath:indexPath animated:NO];
}

Also make sure that in cellForRowAtIndexPath, you have this logic:

...
if (indexPath.row == selectedIndex)
    cell.accessoryType = UITableViewCellAccessoryCheckmark;
else
    cell.accessoryType = UITableViewCellAccessoryNone;
...
return cell;

otherwise, a checkmark will remain on a cell after it scrolls off the screen and comes back on screen even after you've selected another cell.