How to make search bar shrinking effect like default mailbox - ios

Question

How make animation like ios default mail. I need the same effect like search bar is hide at initial and when i drag table view download the it shows the search bar.
like in the screenshot
update to the question.- Right now i am using a searchBar above tableview in the view controller.
var resultSearchController = UISearchController()
self.resultSearchController = ({
let controller = UISearchController(searchResultsController: nil)
controller.searchResultsUpdater = self
controller.dimsBackgroundDuringPresentation = false
controller.searchBar.sizeToFit()
workActivityTableView.tableHeaderView = controller.searchBar
workActivityTableView.contentOffset = CGPoint(x: 0, y: controller.searchBar.frame.height)
navigationController?.extendedLayoutIncludesOpaqueBars = true
return controller
})()

Answer 1

Drag search bar in to your tableview in your storyboard as it should be the first subview of your tableview!
Tableview will consider it as a header.
Your view hierarchy will be look like,
And the default size of search bar will be 44.
Now in your viewDidload set content offset of your table view like,
_tblView.contentOffset = CGPointMake(0, 44);
or in swift you can say,
tblView.contentOffset = CGPoint(x: 0, y: 44)
and you're done!
bellows are screenshot of results,
Initially
After scroll
This will not work if prefersLargeTitles set to true then initially you will get search bar!

Answer 2

I'd suggest you add the search bar as a tableHeaderView to your tableView, and in your viewDidLoad, add the following lines:
tableView.tableHeaderView = your_searchbar
tableView.contentOffset = CGPoint(x: 0, y: your_searchar.frame.height)
navigationController?.extendedLayoutIncludesOpaqueBars = true
UPDATE:
This can be easily achieved by adding the search controller as a part of navigationItem. Something like this:
self.navigationItem.searchController = searchController
This is available from iOS 11.