swift UITabBarController 嵌套 UINavigationController

		//大致相当于 tabar管理3个navigation.
 		tabBarCtrl = UITabBarController()
        let viewHome = ViewHome()
        viewHome.tabBarItem.image = UIImage(systemName: "house")
        viewHome.tabBarItem.title = "组件"
        let viewIcon = ViewIcon()
        viewIcon.tabBarItem.image = UIImage(systemName: "photo.on.rectangle")
        viewIcon.tabBarItem.title = "图标"
        let viewSetting = ViewSetting()
        viewSetting.tabBarItem.image = UIImage(systemName: "gearshape")
        viewSetting.tabBarItem.title = "设置"
        let view1 = UINavigationController.init(rootViewController: viewHome)
        let view2 = UINavigationController.init(rootViewController: viewIcon)
        let view3 = UINavigationController.init(rootViewController: viewSetting)
        
        tabBarCtrl.addChild(view1)
        tabBarCtrl.addChild(view2)
        tabBarCtrl.addChild(view3)
        tabBarCtrl.selectedIndex = 0
        self.window?.rootViewController = tabBarCtrl
        window?.makeKeyAndVisible()