既然完成了第一頁的大部分的要素，那應該就要來建構其他的功能
為了達成這個要素，TabbarView會是我們會用到的元件

建立 tabBarViewController

tabType

在建立tabBarController之前先建立enum來儲存必要的要素

enum tabType {
    case first
    case second
    case third
    case four
    
    var img: String {
        switch self {
        case .first:
            return "personalhotspot"
        case .second:
            return "play.square"
        case .third:
            return "giftcard.fill"
        case .four:
            return "clock.circle.fill"
        }
    }
    
    var title: String {
        switch self {
        case .first:
            return "First"
        case .second:
            return "Second"
        case .third:
            return "Third"
        case .four:
            return "Four"
        }
    }
    
    var vc: Any
}

tabBarController

class tabBarController: UITabBarController {
    let subVC:[tabType] = [.first, .second, .third, .four]
    
    override func viewDidLoad() {
        configure()
    }

    func configure() {
        for i in subVC {
            let vc = UIViewController()
            vc.view.backgroundColor = .white
            vc.tabBarItem.image = UIImage(systemName: "\(i.img)")
            vc.tabBarItem.title = i.title
            // 必須要將VC加入到tabBarController內
            addChild(vc)
        }
    }
}

make rootViewController

因為tabBarView要成為第一個出現的ViewController
所以要指定為rootViewController

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        guard let _ = (scene as? UIWindowScene) else { return }

        guard let windowSence = (scene as? UIWindowScene) else { return }
        window = UIWindow(frame: windowSence.coordinateSpace.bounds)
        window?.windowScene = windowSence

        window?.rootViewController = tabBarController()
        window?.makeKeyAndVisible()
    }

以上就可以簡單創造出TabViewController

坑：
記得要把那些創造出來的VC加入進去childVC，否則那些View是不會顯現