Please help. How can I switch between vc

[Kirill12a]

import UIKit import BATabBarController

class MainViewController: UIViewController, BATabBarControllerDelegate {

override func viewDidLoad() {
    super.viewDidLoad()

    let vc1 = UIViewController()
    let vc2 = UIViewController()
    let vc3 = UIViewController()

    let tabBarItem  = BATabBarItem(image: UIImage(named: "intro1")!, selectedImage: UIImage(named: "intro1")!)
    let tabBarItem2 = BATabBarItem(image: UIImage(named: "intro4")!, selectedImage: UIImage(named: "intro4")!)
    let tabBarItem3 = BATabBarItem(image: UIImage(named: "intro5")!, selectedImage: UIImage(named: "intro5")!)

    let baTabBarController = BATabBarController()
    baTabBarController.viewControllers = [vc1, vc2, vc3]
    baTabBarController.tabBarItems = [tabBarItem, tabBarItem2, tabBarItem3]
    baTabBarController.delegate = self
    self.view.addSubview(baTabBarController.view)
    print("fvsfd")

}

func tabBarController(_ tabBarController: BATabBarController, didSelect: UIViewController) {

}

}