[SWIFT] [Beginner] Implement NavigationBar in code

Introduction

I was researching various things to make an app without using Storyboard, but the navigation bar did not work even if I copied the code on the net.

I hope it helps people who are in the same situation as me, and I will put a solution.

• If there is something wrong with this solution, please point it out.

environment

• Xcode version 12.2
• Swift 5.3.1

Implement a navigation bar without using StoryBoard

First, add the code to SceneDelegate.swift.

SceneDelegate.swift

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
//By default_So rewrite it as a scene
        guard let scene = (scene as? UIWindowScene) else { return }
//firstViewController is the first screen displayed(rootViewController)
        let firstViewController = ViewController()
        let navigationController = UINavigationController(rootViewController: firstViewController)
      
        window = UIWindow(windowScene: scene)
        window?.rootViewController = navigationController
        window?.makeKeyAndVisible()
    }

window has moved from AppDelegate toSceneDelegate in the iOS 13 update, and even if you search, most of the information is adding code to AppDelegate. I think you can think of it as "I used to implement it with AppDelegate, but now I need to describe it in SceneDelegate".

Next, we'll write the code that implements the navigation bar.

ViewController.swift

class ViewController: UIViewController {
    
    var button: UIBarButtonItem!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .white
        title = "First"
        button = UIBarButtonItem(barButtonSystemItem: .fastForward, target: self, action: #selector(click))
        navigationItem.rightBarButtonItem = button
    }
    
    @objc func click() {
        let second = SecondViewController()
        navigationController?.pushViewController(second, animated: true)
    }
    
}

SecondViewController.swift

class SecondViewController: UIViewController {

    var button: UIBarButtonItem!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        title = "Second"
        view.backgroundColor = .systemTeal
        
        button = UIBarButtonItem(barButtonSystemItem: .fastForward, target: self, action: #selector(click))
        navigationItem.rightBarButtonItem = button
    }
    
    @objc func click() {
        let third = ThirdViewController()
        navigationController?.pushViewController(third, animated: true)
    }

}

ThirdViewController.swift

class ThirdViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        title = "Third"
        view.backgroundColor = .purple
    }
}

I tried to put the transition movement twice to give a feeling of movement. By the way, this article is intended to implement a navigation bar, so I won't cover UIWindow or @ objc.

** It looks like this when you actually move it **