以编程方式创建SWRevealViewController

Question

我正在iOS上使用SWRevealViewController创建一个滑出菜单。我没有使用故事板（并以编程方式进行）。但是，左侧栏按钮项目不会显示在屏幕上。

代码段是：

-(void) viewDidLoad {

    [super viewDidLoad];

    MenuViewController *mvc = [[UIStoryboard storyboardWithName:@"Menu" bundle:[NSBundle mainBundle]] instantiateViewControllerWithIdentifier:@"MenuController"];

    UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:self];
    navigationController.navigationItem.leftBarButtonItem = self.settingsBarButtonItem;

    self.revealController = [[SWRevealViewController alloc] initWithRearViewController:mvc frontViewController:navigationController];
    self.revealController.delegate = self;


    AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    appDelegate.window.rootViewController = self.revealController;

}

-(UIBarButtonItem *) settingsBarButtonItem {

    if (!_settingsBarButtonItem ) {
        UIImage *moreImage = [[UIImage imageNamed:@"btn_nav_bar_more"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
        _settingsBarButtonItem = [[UIBarButtonItem alloc] initWithImage:moreImage style:UIBarButtonItemStylePlain target:self.revealController action:@selector(revealToggle:)];

    }

    return _settingsBarButtonItem;
}