title: Remove NSNotification Observer from UITableViewCell
body: <p>I have <code>UIVIewController</code> and In that I have placed <code>UITableView</code><br>
  <code>UITableView</code> Contain cell where cell contains <code>UICollectionView</code><br>
  Each cell has its own collectionView.<br>
  Now, I want to update some rows of collection view of different sections based on tableview header.<br>
  My tableview contains section Header and button inside  </p>
  
  <p>Eg : When I click on TableView header I want to update some of row of its cell's collectionView so here I have using the <code>NSNotification</code> for callToUpdate rows in collectionView (All collectionView Related stuff is placed on cell.m file of <code>UITableView</code>)</p>
  
  <p>But the issue is that as cell scroll , the observer is keep adding and my post notification method called multiple time.</p>
  
  <p>I also wrote code for remove observer but it did not work.</p>