Question

my app has a bug, and i believe its because I’m not reseting the cells content. The apple docs say

The table view’s data source implementation of tableView:cellForRowAtIndexPath: should always reset all content when reusing a cell.

Could someone please explain how to do this, or point me to a tutorial? Thank you in advance!

My cellForRow

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

    cell = [tableView dequeueReusableCellWithIdentifier:identifier];
    if (cell == nil)
     {
         cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier] autorelease];

         addBtn = [[UIButton alloc]init];
         addBtn =[UIButton buttonWithType:UIButtonTypeRoundedRect];
         [addBtn setFrame:CGRectMake(220,10,25,55)];
         [addBtn addTarget:self action:@selector(addLabelText:) forControlEvents:UIControlEventTouchUpInside];
         [addBtn setTitle:@"+" forState:UIControlStateNormal];
         [addBtn setEnabled:YES];
         [cell addSubview:addBtn];

         subBtn = [[UIButton alloc]init];
         subBtn=[UIButton buttonWithType:UIButtonTypeRoundedRect];
         [subBtn setFrame:CGRectMake(260,10,25,55)];
         [subBtn addTarget:self action:@selector(subtractLabelText:) forControlEvents:UIControlEventTouchUpInside];
         [subBtn setTitle:@"-" forState:UIControlStateNormal];
         [subBtn setEnabled:YES];
         [cell addSubview:subBtn];

     } 
    //cellText.hidden=!self.editing;
    cell.textLabel.textColor = [UIColor orangeColor];
    [cell setSelectionStyle:UITableViewCellSelectionStyleNone];
    cell.imageView.image = [imageArray objectAtIndex:indexPath.row];  
    cell.textLabel.text = [number objectAtIndex:indexPath.row];// <------ Is this line in the right place?
    cell.textLabel.text = @"1"; // <---- Is this line in the right place? 


return cell;
}

Answer 1

It’s pretty simple. You provide the call cellForRowAtIndexPath in your code. In it, you either provide a brand new cell, or you reuse a cell that the OS has chucked into memory. Basically, you code looks like this:

    static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}

// Configure the cell...
[[cell textLabel] setText:[pickerData objectAtIndex:indexPath.row]];
 cell.accessoryType = (indexPath.row == currentValueOfIndex ) ? 
    UITableViewCellAccessoryCheckmark : UITableViewCellAccessoryNone;


return cell;

The part under the comment // Configure the cell is where you have to reset your cells content. Since it can either be a new cell, or a recycled cell, it will either have no information, or the information from another cell where it was recycled from. In both cases, you provide the cell’s text and accessories and anything else you want to use each time the cell is called. Basically, it’s a callback to you to provide a cell, either a brand new one, or a recycled one, and you have to stuff the right info for the cell it’s going to be (based on the index path). Hope I made this clear enough.