title: how to get the cell at index path.item - 1 in collection view
body: <p>I want to access the previous cell (index path.item - 1) in my collection view to change some settings there if  some conditions are fulfilled in the  cell at index path.item</p>
  
  <p>By now I tried this: </p>
  
  <pre><code>        let previousCell = collectionView.cellForItem(at: indexPath - 1)
  </code></pre>
  
  <p>But it doesn't work because of the - 1 it is downcast from index path to an integer value. </p>
  
  <p>How do I get this cell?</p>