IndexPathWithOffset

gistfile1.txt

NSIndexPath *IndexPathWithOffset(UITableView *tableView, NSIndexPath *indexPath, NSInteger offset)
{
    if (indexPath.row < 0 || indexPath.section < 0)
    {
        return nil;
    }
    if (offset == 0)
    {
        return indexPath;
    }
    
    NSIndexPath *result = nil;
    NSInteger section = indexPath.section;
    NSInteger row = indexPath.row;
    NSInteger restOffset = offset;
    for (; section >= 0 && section < tableView.numberOfSections; offset > 0 ? ++section : --section)
    {
        NSInteger numberOfRows = [tableView numberOfRowsInSection:section];
        NSInteger newRow = row + restOffset;
        if (newRow >= 0 && newRow < numberOfRows)
        {
            result = [NSIndexPath indexPathForRow:newRow inSection:section];
            break;
        }
        if (offset > 0)
        {
            restOffset -= numberOfRows - row;
            row = 0;
        }
        else
        {
            restOffset += row + 1;
            if (section > 0)
            {
                row = [tableView numberOfRowsInSection:section - 1] - 1;
            }
        }
    }
    return result;
}