顯示NavigationController/NavigationBar和完成返回動作

在要跳轉至下一個ViewController處，創建一個NavigationController，並將下一個VC作爲它的根VC，然後顯示NavigationController（NavigationController中只有一個VC，所以也就是顯示下一個VC）：

    NextViewController *vc = [[NextNViewController alloc] init];
    UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:vc];
    [self presentViewController:navigationController animated:YES completion:^{
    }];

接着，在NextViewController添加返回按鈕，並返回父視圖：

- (void)viewWillAppear:(BOOL)animated {
    UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(goBack)];
    [self.navigationItem setLeftBarButtonItem:backItem];
}

- (void)goBack {
    [self.navigationController dismissViewControllerAnimated:YES completion:^{
    }];
}