get all cells in UITableView

LocationTableViewController.m

//get all UITableViewCell
-(NSArray *)cellsForTableView
{
  UITableView *tableView = self.tableView;
  NSInteger sections = tableView.numberOfSections;
  NSMutableArray *cells = [[NSMutableArray alloc]  init];
  for (int section = 0; section < sections; section++) {
    NSInteger rows =  [tableView numberOfRowsInSection:section];
    for (int row = 0; row < rows; row++) {
      NSIndexPath *indexPath = [NSIndexPath indexPathForRow:row inSection:section];
      UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];//**here, for those cells not in current screen, cell is nil**
      [cells addObject:cell];
    }
  }
  return cells;
}