title: UITableView is jumping when I insert new rows
body: <p>I tried many ways to solve this problem, but I couldn't. My <code>tableView</code> jumps after it loads more data. I call the downloading method in <code>willDisplay</code>:</p>
  
  <pre><code>func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
      let lastObject = objects.count - 1
      if indexPath.row == lastObject {
          page = page + 1
          getObjects(page: page)
      }
  }
  </code></pre>
  
  <p>and insert rows here:</p>
  
  <pre><code>func getObjects(page: Int) {
      RequestManager.sharedInstance.getObjects(page: page, success: { objects in
          DispatchQueue.main.async(execute: {
              self.objects = self.objects + objects
              self.tableView.beginUpdates()
              var indexPaths = [IndexPath]()
              for i in 0...objects.count - 1 {
                  indexPaths.append(IndexPath(row: i, section: 0))
              }
              self.tableView.insertRows(at: indexPaths, with: .bottom)
              self.tableView.endUpdates()
          });
      })
  }
  </code></pre>
  
  <p>So what do I wrong? Why <code>tableView</code> jumps after inserting new rows?</p>