Добавьте это в свой AppDelegate и поэкспериментируйте с ними.Посмотрите, что происходит, и вы узнаете.
@interface AppDelegate : UIResponder <UIApplicationDelegate, UITabBarControllerDelegate>{
}
@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) UITabBarController *tabBarController;
@end
//*****************************************//
.m file
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
UIViewController *viewController1 = [[Categories alloc] initWithNibName:@"Categories" bundle:nil];
UIViewController *viewController2 = [[Coupons alloc] initWithNibName:@"Coupons" bundle:nil];
UIViewController *viewController3 = [[Favourites alloc] initWithNibName:@"Favourites" bundle:nil];
UIViewController *viewController4 = [[AroundMe alloc] initWithNibName:@"AroundMe" bundle:nil];
viewController2.title = NSLocalizedString(@"Coupons", @"Coupons");
viewController2.tabBarItem.image = [UIImage imageNamed:@"coupons.png"];
viewController3.title = NSLocalizedString(@"Favourites", @"Favourites");
viewController3.tabBarItem.image = [UIImage imageNamed:@"favourites.png"];
// UINavigationController *navController1 = [[UINavigationController alloc] initWithRootViewController:viewController1];
UINavigationController *navController1 = [[UINavigationController alloc] initWithRootViewController:viewController1];
UINavigationController *navController2 = [[UINavigationController alloc] initWithRootViewController:viewController2];
UINavigationController *navController3 = [[UINavigationController alloc] initWithRootViewController:viewController3];
UINavigationController *navController4 = [[UINavigationController alloc] initWithRootViewController:viewController4];
self.tabBarController = [[UITabBarController alloc] init];
self.tabBarController.viewControllers = [NSArray arrayWithObjects:navController1,navController2, navController3, navController4, nil];
self.window.rootViewController = self.tabBarController;