title: Search bar not showing up on the navigation bar iOS 11
body: <p>I am pushing a viewController where I want a searchBar, but search bar is not showing at all. Below is the code. Am I missing something?</p>
  
  <pre><code>var searchController = UISearchController(searchResultsController: nil)
  searchController.searchResultsUpdater = self
  searchController.obscuresBackgroundDuringPresentation = false
  searchController.searchBar.placeholder = "Search here..."
  definesPresentationContext = true
  searchController.searchBar.delegate = self
  searchController.searchBar.sizeToFit()
  if #available(iOS 11.0, *) {
  
      self.navigationItem.searchController = searchController
  } else {
      // Fallback on earlier versions
      navigationItem.titleView = searchController.searchBar
      navigationItem.titleView?.layoutSubviews()
  }
  </code></pre>