Get search bar in navigation bar in Swift

Try this

let leftNavBarButton = UIBarButtonItem(customView:Yoursearchbar)
  self.navigationItem.leftBarButtonItem = leftNavBarButton

Update

You keep a lazy UISearchBar property

lazy   var searchBar:UISearchBar = UISearchBar(frame: CGRectMake(0, 0, 200, 20))

In viewDidLoad

searchBar.placeholder = "Your placeholder"
var leftNavBarButton = UIBarButtonItem(customView:searchBar)
self.navigationItem.leftBarButtonItem = leftNavBarButton

If you want to use storyboard
just drag your searchbar as a outlet,then replace the lazy property with your outlet searchbar