-----> Main View Controller ---> Up Bar ---> Bottom ToolBar ---> Three Buttons ---> ContainerView ---> Tab Bar Controller ---> Second Vc on Click of Second Button ---> Third Vc on Click of Third Button 

 private lazy var FirstObject: mainTabController = { // Instantiate View Controller let viewController = self.storyboard?.instantiateViewController(withIdentifier: "mainTabController") as! mainTabController // Add View Controller as Child View Controller self.addChildViewController(viewController) return viewController }() 

private func add(asChildViewController viewController: UIViewController) { // Configure Child View viewController.view.frame = CGRect(x: 0, y: 0, width: self.firstContainer.frame.size.width, height: self.firstContainer.frame.size.height) // Add Child View Controller addChildViewController(viewController) viewController.view.translatesAutoresizingMaskIntoConstraints = true // Add Child View as Subview firstContainer.addSubview(viewController.view) // Notify Child View Controller viewController.didMove(toParentViewController: self) }