README.md

UITabBarViewController

Basic

import UIKit

class ViewController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()
        setupViews()
    }

    func setupViews() {
        view.backgroundColor = .white

        let firstViewController = ViewController1()

        firstViewController.tabBarItem = UITabBarItem(tabBarSystemItem: .search, tag: 0)

        let secondViewController = ViewController2()

        secondViewController.tabBarItem = UITabBarItem(tabBarSystemItem: .more, tag: 1)

        let tabBarList = [firstViewController, secondViewController]

        viewControllers = tabBarList
    }
}

class ViewController1: UIViewController {
    override func viewDidLoad() {
        view.backgroundColor = .red
    }
}

class ViewController2: UIViewController {
    override func viewDidLoad() {
        view.backgroundColor = .blue
    }
}

How to specify which ViewController to show?

You can programatically specify which ViewController you would to like to appear or navigate to like this.

selectedViewController is a property inside UITabBarViewController and you just specifiy the one you want there.

tabBarController.selectedIndex = 0 or you can specify the index as so.

selectedViewController = secondViewController

TabBar vs NavBar

You can either embed a TabBar in a NavBar or a NavBar in a TabBar - it's completely up to you.

NavBar within a TabBar

Simply create your ViewControllers (one of which can be a NavigationController and add them to your TabBar.

import UIKit

class ViewController1: UIViewController {
    override func viewDidLoad() {
        view.backgroundColor = .systemRed
    }
}

class ViewController2: UIViewController {
    override func viewDidLoad() {
        view.backgroundColor = .systemBlue
    }
}

class ViewController3: UIViewController {
    override func viewDidLoad() {
        view.backgroundColor = .systemGreen
        title = "ViewController3"
    }
}

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.makeKeyAndVisible()
        window?.backgroundColor = .systemBackground
                
        let vc1 = ViewController1()
        vc1.tabBarItem = UITabBarItem(tabBarSystemItem: .search, tag: 0)

        let vc2 = ViewController2()
        vc2.tabBarItem = UITabBarItem(tabBarSystemItem: .contacts, tag: 1)

        let vc3 = ViewController3()
        vc3.tabBarItem = UITabBarItem(tabBarSystemItem: .favorites, tag: 2)
        
        let navController = UINavigationController(rootViewController: vc3)
        
        let tabBarController = UITabBarController()
        tabBarController.viewControllers = [vc1, vc2, navController]

        window?.rootViewController = tabBarController
        
        return true
    }
}

TabBar within a NavBar

Simply reverse who gets embedded within whom. Little less screen real estate this way.

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.makeKeyAndVisible()
        window?.backgroundColor = .systemBackground
                
        let vc1 = ViewController1()
        vc1.tabBarItem = UITabBarItem(tabBarSystemItem: .search, tag: 0)

        let vc2 = ViewController2()
        vc2.tabBarItem = UITabBarItem(tabBarSystemItem: .contacts, tag: 1)

        let vc3 = ViewController3()
        vc3.tabBarItem = UITabBarItem(tabBarSystemItem: .favorites, tag: 2)
        
        let tabBarController = UITabBarController()
        tabBarController.viewControllers = [vc1, vc2, vc3]
        
        let navController = UINavigationController(rootViewController: tabBarController)

        window?.rootViewController = navController
        
        return true
    }
}

How to set the title of the nav bar on a view controller within a tab bar

The title of the nav bar is tied to the title of the tab bar button. You can't set it via title. Instead do it like this.

    private func setupNavBar() {
        navigationController?.navigationBar.topItem?.title = "Good afternoon, Jonathan ☀️"
//        title = "Good afternoon, Jonathan ☀️"
    }

Links that help

• Apple docs
• TabBar vs NavBar Apple
• How To: Working With Tab Bar Controllers In Swift