问如何创建一个包含两个视图的UIViewController，根据单击的按钮显示一个或另一个视图

EN

 - (void)viewDidLoad {
    [super viewDidLoad];
    UIViewController *viewController = [self viewControllerForSegmentIndex:self.typeSegmentedControl.selectedSegmentIndex];
    [self addChildViewController:viewController];
    viewController.view.frame = self.contentView.bounds;
    [self.contentView addSubview:viewController.view];
    self.currentViewController = viewController;
}
- (UIViewController *)viewControllerForSegmentIndex:(NSInteger)index {
    UIViewController *viewController;
    switch (index) {
        case 0:
            viewController = [self.storyboard instantiateViewControllerWithIdentifier:@"FirstViewController"];
            break;
        case 1:
            viewController = [self.storyboard instantiateViewControllerWithIdentifier:@"SecondViewController"];
            break;
    }
    return viewController;
}
- (IBAction)segmentChanged:(UISegmentedControl *)sender {
    UIViewController *viewController = [self viewControllerForSegmentIndex:sender.selectedSegmentIndex];
    [self addChildViewController:viewController];
    [self transitionFromViewController:self.currentViewController toViewController:viewController duration:0.0 options:UIViewAnimationOptionTransitionNone animations:^{
        [self.currentViewController.view removeFromSuperview];
        viewController.view.frame = self.contentView.bounds;
        [self.contentView addSubview:viewController.view];
    } completion:^(BOOL finished) {
        [viewController didMoveToParentViewController:self];
        [self.currentViewController removeFromParentViewController];
        self.currentViewController = viewController ;
    }];
    self.navigationItem.title = viewController.title;
}