iOS Root view controller architecture example

gistfile1.m

@interface RootViewController : UIViewController

// Child view controllers
@property (nonatomic) MenuViewController *menuViewController; // Hamburger menu
@property (nonatomic) UINavigationController *mainNavigationController; // Main UI

- (void)presentTutorial; // Or first time user registration, etc. Called from the app delegate.

@end

@implementation RootViewController

- (void)menuViewController:(MenuViewController *)menuViewController didPickMenuItem:(MenuItem *)menuItem {

  UIViewController *viewController = [self viewControllerForMenuItem:menuItem]; // Instanciation and caching here 
  
  // Root view controller sets hamburger bar button item on child
  // to decouple content view controllers from the larger app navigation
  viewController.navigationItem.leftBarButtonItem = [self hamburgerMenuItem];
  
  self.mainNavigationController.rootViewController = viewController;

  [self closeMenuAnimated:YES];
}

- (UIBarButtonItem *)hamburgerMenuItem {

  return [[UIBarButtonItem alloc] initWithTitle:@"Menu" style:UIBarbuttonItemStylePlain target:self selector:@selector(toggleMenu)];
}

@end