如何让NavigationItem.searchController的searchBar使用整个屏幕的宽度

class SearchController: UISearchController {
    override init(searchResultsController: UIViewController?) {
        super.init(searchResultsController: searchResultsController)
        self.searchBar.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: 44)
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
}

let searchController = SearchController(searchResultsController: nil)
navigationItem.searchController = searchController

override func viewDidLoad() {
    super.viewDidLoad()
    definesPresentationContext = true
}