gistfile1.m

# AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
    
    [[AuthenticationManager sharedInstance] setupWithWindow:self.window];
    
    return YES;
}

# AuthenticationManager.m

- (UIViewController *)loginViewController
{
    if (_loginViewController) return _loginViewController;
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"LPiPhone" bundle:nil];
    _loginViewController = [storyboard instantiateViewControllerWithIdentifier:@"LoginViewController"];
    return _loginViewController;
}

- (void)setupWithWindow:(UIWindow *)window
{
    self.window = window;
    
    if (![[SessionManager sharedInstance] loggedIn])
        [self showLoginScreen:NO];
}

- (void)showLoginScreen:(BOOL)animated
{
    NSInteger transition = animated ? UIViewAnimationOptionTransitionFlipFromRight : UIViewAnimationOptionTransitionNone;
    [UIView transitionWithView:self.window duration:0.5 options:transition|UIViewAnimationOptionAllowAnimatedContent animations:^{
        self.window.rootViewController = [self loginViewController];
    } completion:nil];
}

# SessionManager.m

- (BOOL)loggedIn
{
    return [self.authenticationToken length] > 0;
}