Switching root view controller - ios

Question

I've an app with UINavigationController already, but i want to switch to UITabBarController, the problem is when i switch to UItab from beginning it doesn't work, so i'm switching it in a delegate method but it doesn't work either!
all code in the app delegate.
self.navigationController = [[UINavigationController alloc] initWithRootViewController:[[UIViewController alloc] init]];
self.tabBarController = [[UITabBarController alloc] init];
if ([PFUser currentUser]) {
// Present wall straight-away
[self presentWallViewControllerAnimated:NO];
} else {
// Go to the welcome screen and have them log in or create an account.
[self presentLoginViewController];
}
[PFAnalytics trackAppOpenedWithLaunchOptions:launchOptions];
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];
The delegate method i want to switch on it:
- (void)presentWallViewControllerAnimated:(BOOL)animated {
NSLog(#"Called:presentWallViewControllerAnimated ");
// self.navigationController = nil;
self.tabBarController = [[UITabBarController alloc] init];
PAWWallViewController *wallViewController = [[PAWWallViewController alloc] initWithNibName:nil bundle:nil];
wallViewController.delegate = self;
// Set up the first View Controller
UIViewController *vc1 = [[UIViewController alloc] init];
vc1.view.backgroundColor = [UIColor orangeColor];
vc1.tabBarItem.title = #"Orange";
vc1.tabBarItem.image = [UIImage imageNamed:#"heart"];
// Set up the second View Controller
UIViewController *vc2 = [[UIViewController alloc] init];
vc2.view.backgroundColor = [UIColor purpleColor];
vc2.tabBarItem.title = #"Purple";
vc2.tabBarItem.image = [UIImage imageNamed:#"star"];
// Set up the Tab Bar Controller to have two tabs
[self.tabBarController setViewControllers:#[ vc1, vc2]];
self.window.rootViewController = self.tabBarController;
[self.window makeKeyAndVisible];
// [self.window addSubview:tabBarController.view];
// [self.navigationController setViewControllers:#[ tabBarController ] animated:animated];
}

Answer 1

Remember to handle the view transition:
UIViewController *vc = // any vc that's initialized properly
window.rootViewController = vc;
[UIView transitionWithView:window
duration:0.3 // 0.0 for immediate
options:UIViewAnimationOptionTransitionCrossDissolve // several enums to choose from here
animations:nil
completion:nil];
and you don't need makeKeyAndVisible after the first time.

Answer 2

You called - (void)presentWallViewControllerAnimated:(BOOL)animated but in the end of didFinishLaunchingWithOptions you called
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];
So the tab bar will never works !