把子控制器添加到导航控制器中的四种方法

    ViewController *vc = [[ViewController alloc]init];//    UINavigationController *nav = [[UINavigationController alloc] init];//    [nav addChildViewController:vc];        UINavigationController *nav = [[UINavigationController alloc]initWithRootViewController:vc];    //    UINavigationController *nav = [[UINavigationController alloc]init];//    [nav pushViewController:vc animated:YES];        //    UINavigationController *nav = [[UINavigationController alloc]init];//    nav.viewControllers = @[vc];//添加到导航控制器的栈中,//                self.window.rootViewController = nav;