怎么获取被选中cell的下一个cell？

我想在一个cell被选中时改变下一个cell的detailtable；

我试了下面的方法

     NSIndexPath *indexPath = [.myTableView indexPathForSelectedRow];
        UITableViewCell *cell =［.myTableView cellForRowAtIndexPath:indexPath]
                NSUInteger i = indexPath.row +1;
                   NSIndexPath *nextCellIndexPath = [NSIndexPath indexPathWithIndex:i];
                    UITableViewCell *nextCell = [addOperationViewController.myTableView cellForRowAtIndexPath:nextCellIndexPath];

但是报错
Assertion failure in -[NSIndexPath row], /SourceCache/UIKit_Sim/UIKit-3318.16.14/UITableViewSupport.m:2813
2015-03-11 21:46:19.544 Project[8647:228767] * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid index path for use with UITableView. Index paths passed to table view must contain exactly two indices specifying the section and row. Please use the category on NSIndexPath in UITableView.h if possible.'

请问怎么解决？

写错了：
NSIndexPath *ipath = [tableView indexPathForSelectedRow];
UITableViewCell *cell = [tableView cellForRowAtIndexPath:ipath];
NSUInteger i = ipath.row +1;
NSIndexPath *nextCellIndexPath = [NSIndexPath indexPathForRow:i inSection:0];//这里的问题
UITableViewCell *nextCell = [tableView cellForRowAtIndexPath:nextCellIndexPath];