如何以编程方式在UINavigationController的左栏按钮项目中显示UISearchController，并在搜索后隐藏它？

let searchController = UISearchController(searchResultsController: nil)
searchController.searchResultsUpdater = self

navigationItem.titleView = searchController.searchBar

searchController.searchBar.placeholder = "搜索"
searchController.searchBar.barTintColor = UIColor.white

let searchButton = UIBarButtonItem(barButtonSystemItem: .search, target: self, action: #selector(showSearchController))
navigationItem.leftBarButtonItem = searchButton

@objc func showSearchController() {
    navigationItem.titleView = searchController.searchBar
    navigationItem.setLeftBarButton(nil, animated: true)
    searchController.isActive = true
}

func updateSearchResults(for searchController: UISearchController) {
    // 处理搜索结果更新的逻辑
    
    if !searchController.isActive {
        navigationItem.titleView = nil
        navigationItem.leftBarButtonItem = searchButton
    }
}