title: Update CollectionView supplementaryView header when off screen
body: <p>I have a view similar to Instagram's main stories feed. I have a horizontal collection view at the top where I have a supplementaryView header cell that looks the same but acts differently to the rest of the cells. </p>
  
  <p>I am trying to update the objects in the supplementaryView which I have managed to do with the following code...</p>
  
  <pre><code>@objc func uploadCompleted() {
  
      DispatchQueue.main.async {
          self.collectionView.performBatchUpdates({
              if let myCell = self.collectionView.supplementaryView(forElementKind: UICollectionElementKindSectionHeader, at: IndexPath(item: 0, section: 0)) as? MyCollectionReusableView {
                  // Do your stuff here
                  myCell.nameLbl.textColor = .black
                  ...
              }
          }, completion: nil)
      }
  }
  </code></pre>
  
  <p>This works fine when the cell is in view, however when the cell is swiped off screen during this call it doesn't get updated.</p>
  
  <p>Any ideas on how to get around this? Or a better approach to updating just the first cell in a collection view and not the rest.</p>
  
  <p>Thanks</p>