(iOS) Initializing View Controllers. Delegate file - Single & Multi View examples

MultiAppDelegate.mm

//Import your root controller to the .h

//And set your property of your controller
//@property (strong, nonatomic) BIDViewController *switchViewController;

@implementation BIDAppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    //Create the main window screen
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    
    /*****************************************************************************************/
    //intialize the root controller, with the the controller's nib name file.
    self.switchViewController = [[BIDSwitchViewController alloc] initWithNibName:@"SwitchView" bundle:nil];

    //If you need to change the view’s geometry so it does not get hidden behind the status bar.
    UIView *switchView = self.switchViewController.view;
    CGRect switchViewFrame = switchView.frame;
    switchViewFrame.origin.y += [UIApplication sharedApplication].statusBarFrame.size.height;
    switchView.frame = switchViewFrame;
    //Geometry changed    

    //Make switchViewController the root controller
    self.window.rootViewController = self.switchViewController;
    /*****************************************************************************************/
    
    //If you want to change the background color
    self.window.backgroundColor = [UIColor whiteColor];
    
    //Already there
    [self.window makeKeyAndVisible];
    return YES;
}

//HERE WE HAVE TO PUT CODE TO THE ROOT CONTROLLER SO IT LOADS SUBVIEWS OF THE OTHER
//CONTROLLERS WE WANT TO SHOW, IN THE viewDidLoad METHOD
//.
//SEE switchViewController.mm BELOW

SingleAppDelegate.mm

//Import your controller to the .h

//And set your property of your controller
//@property (strong, nonatomic) BIDViewController *viewController;

@implementation BIDAppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    //Create the main window screen
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    //Initialize the controller
    self.viewController = [[BIDViewController alloc] initWithNibName:@"BIDViewController" bundle:nil];

    //Set the root Controller to your root controller if any
    self.window.rootViewController = self.viewController;

    //Already there
    [self.window makeKeyAndVisible];
    return YES;
}

switchViewController.mm

/**************************************************************
Import all your controllers with their properties

ex. of 2 view controllers
@property (strong, nonatomic) BIDYellowViewController *yellowViewController;
@property (strong, nonatomic) BIDBlueViewController *blueViewController;
**************************************************************/

- (void)viewDidLoad
{
    [super viewDidLoad];
  // Do any additional setup after loading the view.
    
    /*******************************************************************/
    //Override a UIViewController method that is called when the nib is loaded
    
    self.blueViewController = [[BIDBlueViewController alloc] initWithNibName:@"BlueView" bundle:nil];
    
    //Insert it as a subview of the root view so the toolbar will be shown
    [self.view insertSubview:self.blueViewController.view atIndex:0];
    /*******************************************************************/
    
}

switchViewsAction.mm

//Action that switches between 2 views

//Here free any memory you can by adding code to this method
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
    
    /*******************************************************************/
    //Check which view is shown and release the other one
    if (self.blueViewController.view.superview == nil)
    {
        //Release the controller by adding nil at its property
        self.blueViewController = nil;
    }
    else
    {
        self.yellowViewController = nil;
    }
    /*******************************************************************/

}

//The actual action
- (IBAction)switchViews:(id)sender
{
    //Animate the transition
    [UIView beginAnimations:@"View Flip" context:nil];
    [UIView setAnimationDuration:1.25];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    
    //Check if yellowView is showing. Either not loaded at all or
    //not in the view hierarchy, since it won't have a superview
    if (self.yellowViewController.view.superview == nil)            //if not
    {
        //If yellowView hasn't been loaded yet, load it
        if (self.yellowViewController == nil)
        {
            self.yellowViewController = [[BIDYellowViewController alloc] initWithNibName:@"YellowView" bundle:nil];
        }
        
        [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES];
        
        //Remove bluw view
        [self.blueViewController.view removeFromSuperview];
        
        //Show yellowView
        [self.view insertSubview:self.yellowViewController.view atIndex:0];
    }
    else    //else the opposite
    {
        if (self.blueViewController == nil)
        {
            self.blueViewController =
            [[BIDBlueViewController alloc] initWithNibName:@"BlueView" bundle:nil];
        }
        
        [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:self.view cache:YES];
        
        [self.yellowViewController.view removeFromSuperview];
        [self.view insertSubview:self.blueViewController.view atIndex:0];
    }
    
    [UIView commitAnimations];
}

[self.view addSubview:self.ViewController.view];

---

There are also:

[self.view sendSubviewToBack:self.ViewController.view]

and

[self.view bringSubviewToFront.ViewController.view]

to manage which one the user sees, if you have to keep both views around without destroying them