Position of UISearchBar moving down when clicked on iOS10 - ios

Question

I have a trouble with a search bar only on iOS 10 (it works well on iOS 11) and I don't know what's going on, it's been several days I'm trying to solve this by myself without success so I hope someone here could tell me what I do wrong.
So, initially, my screen is like this
And when I click in the search bar, it goes like that
If I type text, it well displays the results under the search bar. I just don't know where this space between my search bar and the navigation bar comes from.
The results of my search is managed by an another viewcontroller declared like this.
let locationSearchTable = storyboard!.instantiateViewController(withIdentifier: "LocationSearchTableViewController") as! LocationSearchTableViewController
resultSearchController = UISearchController(searchResultsController: locationSearchTable)
resultSearchController?.searchResultsUpdater = locationSearchTable
A bit of my code, especially where I set up the search bar:
let searchBar = resultSearchController!.searchBar
searchBar.sizeToFit()
searchBar.placeholder = "Search for a place or address"
if #available(iOS 11.0, *) {
navigationItem.searchController = resultSearchController
resultSearchController?.dimsBackgroundDuringPresentation = true
} else {
searchBar.delegate = self
searchBar.searchBarStyle = .default
searchBar.setShowsCancelButton(false, animated: true)
searchBar.keyboardAppearance = .default
navigationController?.navigationBar.isTranslucent = false
searchBar.isTranslucent = false
resultSearchController?.dimsBackgroundDuringPresentation = false
mainView.addSubview(searchBar)
}
definesPresentationContext = true
resultSearchController?.hidesNavigationBarDuringPresentation = false
}

Answer 1

For others who might encounter the same issue, here is my code now and it's working.
let searchBar = resultSearchController!.searchBar
searchBar.sizeToFit()
searchBar.placeholder = "Search for a place or address"
if #available(iOS 11.0, *) {
navigationItem.searchController = resultSearchController
resultSearchController?.hidesNavigationBarDuringPresentation = false
resultSearchController?.dimsBackgroundDuringPresentation = true
} else {
searchBar.searchBarStyle = .default
searchBar.setShowsCancelButton(false, animated: true)
searchBar.keyboardAppearance = .default
navigationController?.navigationBar.isTranslucent = false
searchBar.barStyle = .default
searchBar.isTranslucent = false
resultSearchController?.hidesNavigationBarDuringPresentation = true
resultSearchController?.dimsBackgroundDuringPresentation = false
UI_mapView.addSubview(searchBar)
}
definesPresentationContext = true
let currentLocationButtonItem = MKUserTrackingBarButtonItem(mapView: UI_mapView)
self.navigationItem.rightBarButtonItem = currentLocationButtonItem