Swift: Setting Different Navigation Bar Buttons for Different Tabs - ios

Question

I created a custom UITabBarController with 5 tabs in Swift 3.0. I've been trying to set different navigation bar items for certain tabs, but it's not working well.
Situation: I put codes that would change the Navigation Bar Buttons in each tab's viewDidLoad().
//The customized Tab Bar controller instance. Contained in each of the tabs.
var mainController: TabBarController?
override func viewDidLoad() {
// ... more code
setupNavBar()
// ... more code
}
func setupNavBar() {
// ... more code
mainController?.navigationItem.leftBarButtonItem = UIBarButtonItem(image: friendsImage, style: .plain, target: self, action: #selector(handleFindFriends))
// ... more code
}
Problem: Let's say Tab #1 is supposed to have NavBarButton A and Tab #2 is supposed to have NavBarButton B.
When I switch from Tab #1 to Tab #2, the code works fine; the NavBarButton changes from A to B.
However, when I click on Tab #1, the NavBarButton still remains B.
How can I make it so that the navigation bar buttons change accordingly even when I click on a tab I was on previously?

Answer 1

I assume you embed a UITabBarController (or it's subclass) into a UIViewController. This is wrong because in this case you tend to make the view controller generic which is usually a bad practice.
Instead I would suggest to change hierarchy of view controller to what you see on the image below.
UPDATE
If you do it in code:
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
let tabBarController = UITabBarController()
// first tab
let firstViewController = UIViewController()
_ = firstViewController.view
firstViewController.title = "First"
let firstNavigationController = UINavigationController(rootViewController: firstViewController)
// sets a specific button ("Friends") on a navigation bar for the first screen
firstViewController.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Friends", style: .plain, target: nil, action: nil)
// second tab
let secondViewController = UIViewController()
_ = secondViewController.view
secondViewController.title = "Second"
let secondNavigationController = UINavigationController(rootViewController: secondViewController)
// sets a specific button ("Photos") on a navigation bar for the second screen
secondViewController.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Photos", style: .plain, target: nil, action: nil)
// embeds the navigation controllers into the tab bar controller
tabBarController.viewControllers = [firstNavigationController, secondNavigationController]
// creates a window with the tab bar controller inside
window = UIWindow(frame: UIScreen.main.bounds)
window?.rootViewController = tabBarController
window?.makeKeyAndVisible()
return true
}
}

Answer 2

I actually found a solution XD
In TabBarController:
override func viewWillAppear(_ animated: Bool) {
//Original code to set up tabs
//Code I added:
for i in 0...4 {
tabBar.items?[i].tag = i
}
}
//Code I added:
override func tabBar(_ tabBar: UITabBar, didSelect item: UITabBarItem) {
//Code to run when a certain tab is selected
}
Still, thanks a lot!