title: insertSections in tableView
body: <p>I want to insert some section after update but I have the same elements. How can I do it? I want to inset elements after last element. But have error.</p>
  
  <p>My code </p>
  
  <pre><code>     [self.tableView beginUpdates];
       for (WallPost *wp in news) {
          if (!_tableDataSource.count || ![_tableDataSource containsObject:wp]) {
             [_tableDataSource insertObject:wp atIndex:_tableDataSource.count];
             [self.tableView insertSections:
                 [NSIndexSet indexSetWithIndex:
                 _tableDataSource.count-1] 
                 withRowAnimation:UITableViewRowAnimationBottom];
          }
       }
       [self.tableView endUpdates];
  </code></pre>