关于ios：如何用代码将UISearchController搜索栏放在导航栏上

How do I put UISearchController Searchbar onto navigation bar with code

如果我将 ViewController 嵌入到导航栏中，navigationItem.titleView.resultSearchController?.searchBar 会将搜索栏放入导航栏中。但是，我用代码创建了一个 UISearchController 和一个 UINavigationBar。这一次，navBar 出现了，但 searchBar 没有出现。

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resultSearchController = UISearchController(searchResultsController: locationSearchTable)
resultSearchController?.searchResultsUpdater = locationSearchTable

let searchBar = resultSearchController!.searchBar
searchBar.sizeToFit()
searchBar.delegate = self

let navBar: UINavigationBar = UINavigationBar(frame: CGRect(x: 0, y:0, width: 375, height: 64))
self.view.addSubview(navBar)
//navBar.topItem = resultSearchController?.searchBar
self.navigationItem.titleView = resultSearchController?.searchBar

navBar.topItem = resultSearchController?.searchBar 不起作用，因为 topItem 是字符串值，而 resultSearchController?.searchBar 是 UIView 类型。我怎样才能达到同样的效果？

创建一个 UINavigationItem 实例并将其添加到创建的导航栏。
将搜索控制器搜索栏添加到 UINavigationItem 作为 titleView.

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class SearchViewController: UIViewController, UISearchControllerDelegate, UISearchResultsUpdating, UISearchBarDelegate {

var searchController: UISearchController!

override func viewDidLoad() {
super.viewDidLoad()
self.addNavigationbar()
}

func addNavigationbar() {
let navBar = UINavigationBar(frame: CGRect(x: 0, y: 0, width: self.view.frame.size.width, height: 60))
self.view.addSubview(navBar)

let navigationItem = UINavigationItem(title:"")
self.searchController = searchControllerWith(searchResultsController: nil)
navigationItem.titleView = self.searchController.searchBar

navBar.setItems([navigationItem], animated: false)
self.definesPresentationContext = true
}

func searchControllerWith(searchResultsController: UIViewController?) -> UISearchController {

let searchController = UISearchController(searchResultsController: searchResultsController)
searchController.delegate = self
searchController.searchResultsUpdater = self
searchController.searchBar.delegate = self
searchController.hidesNavigationBarDuringPresentation = false
searchController.dimsBackgroundDuringPresentation = true

return searchController
}

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class UIViewController: UIViewController, UISearchControllerDelegate, UISearchResultsUpdating, UISearchBarDelegate {

var searchController : UISearchController!

override func viewDidLoad() {
super.viewDidLoad()

self.searchController = UISearchController(searchResultsController: nil)

self.searchController.searchResultsUpdater = self
self.searchController.delegate = self
self.searchController.searchBar.delegate = self

self.searchController.hidesNavigationBarDuringPresentation = false
self.searchController.dimsBackgroundDuringPresentation = true

self.navigationItem.titleView = searchController.searchBar

self.definesPresentationContext = true
}

func updateSearchResults(for searchController: UISearchController) {

}

}