UIViewController不保留其以编程方式创建的UISearchDisplayController

class MyViewController: UIViewController {
    var searchDisplayController: UISearchDisplayController?

    override func viewDidLoad() {
        super.viewDidLoad()

        let searchBar = UISearchBar()
        searchDisplayController = UISearchDisplayController(searchBar: searchBar, contentsController: self)
        searchDisplayController?.delegate = self
        searchDisplayController?.searchResultsDataSource = self
        searchDisplayController?.searchResultsDelegate = self
    }
}

extension MyViewController: UISearchDisplayDelegate, UISearchResultsDataSource, UISearchResultsDelegate {
    // Implement the required methods here
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    if let searchDisplayController = searchDisplayController {
        view.addSubview(searchDisplayController.view)
    }
}