Fade animation in tab bar controller

tab_controller_fading.swift

func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
        animateFading(fromController: selectedViewController, toController: viewController)
        return true
    }
    
    func animateFading(fromController: UIViewController?, toController: UIViewController?) {
        if fromController == nil || toController == fromController { return }

        guard let selectView = (selectedViewController as? UINavigationController)?.viewControllers.first?.view,
            let newView = (toController as? UINavigationController)?.viewControllers.first?.view else { return }

        let fromView = selectView
        let toView = newView

        UIView.transition(from: fromView, to: toView, duration: 0.35, options: [.transitionCrossDissolve], completion: nil)
    }