RxSwift only trigger once

Question

searchController.searchBar.rx.text
            .asDriver()
            .map{ $0 == "" || $0 == nil }
            .drive(onNext: { (empty) in
                if empty {
                    print("Search empty")
                } else {
                    print("!!!!!!!!!!!!! empty")
                }
            }).disposed(by: disposeBag)

This will be called once the first time it is started, the second one when I type the first string, but will not be valid anymore，where the error? thank!!!

Answer 1

I have checked your code and found that setting UISearchBar's delegate makes the driver to fire only once. For example:

self.searchController.searchBar.delegate = self

If the delegate isn't set - the driver fires as you expect. So you should do something with search delegates and check whether it helps you to solve the problem.

This is a sample project which represents this behavior:

import Foundation
import UIKit
import RxCocoa
import RxSwift

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow? = UIWindow(frame: UIScreen.main.bounds)

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        window?.rootViewController = UINavigationController(rootViewController: Controller())
        window?.makeKeyAndVisible()
        return true
    }
}

final class Controller: UIViewController, UISearchResultsUpdating, UISearchControllerDelegate, UISearchBarDelegate {

    lazy var disposeBag = DisposeBag()
    lazy var searchController = UISearchController(searchResultsController: nil)

    init() {
        super.init(nibName: nil, bundle: nil)
        self.view.backgroundColor = UIColor.orange
        self.searchController.searchResultsUpdater = self
        self.searchController.hidesNavigationBarDuringPresentation = false
        self.navigationItem.titleView = self.searchController.searchBar
        self.definesPresentationContext = true
        self.searchController.delegate = self
        self.searchController.dimsBackgroundDuringPresentation = false
        // self.searchController.searchBar.delegate = self
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        searchController.searchBar.rx.text
            .asDriver()
            .map{ $0 == "" || $0 == nil }
            .drive(onNext: { (empty) in
                if empty {
                    print("Search empty")
                } else {
                    print("!!!!!!!!!!!!! empty")
                }
            })
            .disposed(by: disposeBag)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func updateSearchResults(for searchController: UISearchController) {
        //
    }
}