SDKs
- iOS 10.0+
- Xcode 11.0+
Framework
- Foundation
Overview
This sample demonstrates how to create a table view controller and search controller to manage the display of searchable content. It creates another custom table view controller to display the search results. This table view controller also acts as the presenter or provides context for the search results so they’re presented within their own context.
This sample includes the optional—but recommended—UIState
protocol. You adopt this protocol from the view controller class to save the search bar’s active state, first responder status, and search bar text and restore them when the app is relaunched.
Create a Search Controller
Use Main
, a subclass of UITable
, to create a search controller. The search controller searches and filters a set of Product
objects and displays them in a table called Results
. This table controller is displayed as the user enters a search string and is dismissed when the search is complete.
There are two ways to create the search controller in Main
, depending on the iOS version. In iOS 10 and earlier, you place it inside the table view’s header. In iOS 11 and later, you place it in the view controller’s navigation bar.
override func viewDidLoad() {
super.viewDidLoad()
resultsTableController = ResultsTableController()
resultsTableController.tableView.delegate = self
searchController = UISearchController(searchResultsController: resultsTableController)
searchController.searchResultsUpdater = self
searchController.searchBar.autocapitalizationType = .none
if #available(iOS 11.0, *) {
// For iOS 11 and later, place the search bar in the navigation bar.
navigationItem.searchController = searchController
// Make the search bar always visible.
navigationItem.hidesSearchBarWhenScrolling = false
} else {
// For iOS 10 and earlier, place the search controller's search bar in the table view's header.
tableView.tableHeaderView = searchController.searchBar
}
searchController.delegate = self
searchController.dimsBackgroundDuringPresentation = false // The default is true.
searchController.searchBar.delegate = self // Monitor when the search button is tapped.
/** Search presents a view controller by applying normal view controller presentation semantics.
This means that the presentation moves up the view controller hierarchy until it finds the root
view controller or one that defines a presentation context.
*/
/** Specify that this view controller determines how the search controller is presented.
The search controller should be presented modally and match the physical size of this view controller.
*/
definesPresentationContext = true
}
Update the Search Results
This sample uses the UISearch
protocol, along with NSComparison
, to filter out search results from the group of available products. NSComparison
is a foundation class that specifies how data should be fetched or filtered using search criteria. The search criteria are based on what the user types in the search bar, which can be a combination of product title, year introduced, and price.
To prepare for a search, the search bar content is trimmed of all leading and trailing space characters. Then the search string is passed to the find
function, which returns the NSComparison
used in the search. The product list results are applied to the search results table as a filtered list.
func updateSearchResults(for searchController: UISearchController) {
// Update the filtered array based on the search text.
let searchResults = products
// Strip out all the leading and trailing spaces.
let whitespaceCharacterSet = CharacterSet.whitespaces
let strippedString =
searchController.searchBar.text!.trimmingCharacters(in: whitespaceCharacterSet)
let searchItems = strippedString.components(separatedBy: " ") as [String]
// Build all the "AND" expressions for each value in searchString.
let andMatchPredicates: [NSPredicate] = searchItems.map { searchString in
findMatches(searchString: searchString)
}
// Match up the fields of the Product object.
let finalCompoundPredicate =
NSCompoundPredicate(andPredicateWithSubpredicates: andMatchPredicates)
let filteredResults = searchResults.filter { finalCompoundPredicate.evaluate(with: $0) }
// Apply the filtered results to the search results table.
if let resultsController = searchController.searchResultsController as? ResultsTableController {
resultsController.filteredProducts = filteredResults
resultsController.tableView.reloadData()
}
}