title: UICollectionViewDataSource methods are not getting called when data-source is a separate class
body: <p>I created a <code>UICollectionView</code> inside a <code>UITableViewCell</code> and a separate data-source class <code>DataSource</code> for this collection-view.</p>
  
  <p><code>DataSource</code> conforms to the <code>UICollectionViewDataSource</code> protocol and I have also assigned the <code>dataSource</code> of an instance of <code>DataSource</code> in my collection-view container class.</p>
  
  <p>But none of the data-source methods in <code>DataSource</code> are getting called.</p>
  
  <p><em>It was working fine before I created a separate class for <code>UICollectionView</code> data-source.</em></p>