Which method called when appdelegate.m transfers control to viewController - objective-c

Question

I learn the ObjC program flow, so far I understand that chain begins in main.m->UIApplicationMain->AppDelegate->ViewController
The point I don't understand is to which method inside the ViewController the AppDelegate class transfers the focus...
I feel it is critical to understand this topic, so would be thankful for any clarifications.
I have this code of Appdelegate.m -
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions: (NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
MasterViewController *masterViewController = [[MasterViewController alloc] init];
self.navigationController = [[UINavigationController alloc] initWithRootViewController: masterViewController];
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];
return YES;
and inside the ViewController there are these methods -
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self.navigationController setNavigationBarHidden:YES animated: NO];
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear: animated];
}
and others methods...
My questions are
To what method AppDelegate transfers control in MasterViewController. And does the control come back after MasterViewController "finished" its job or it is just looped?
How MasterViewController gets the xib name for initialisation (is it the same name as m file? i.e. what does it mean - nibNameOrNil bundle:nibBundleOrNil)
I see navigation controller involvement, however I don't understand how it is connected to viewcontroller....
If you catch my misunderstanding points - please be patient to explain... I feel that after this point I will be able to start...

Answer 1

(1) You're thinking about the logical flow in a procedural sort of way. The main run loop dispatches events down the responder chain. Your MasterViewController doesn't really 'finish'.
(2) The designated initializer for UIViewController is initWithNibName:bundle:. Your use of init here will not touch any associated nib file. If you wish to initialize MasterViewController from the nib, then you must use the designated initializer, e.g.
MasterViewController *masterViewController = [[MasterViewController alloc] initWithNibName:#"your-nib-name-goes-here" bundle:nil];
nibNameOrNil and nibBundleOrNil are just parameter names for the method. It's a tip to you that they may be nil. Take a look at the documentation for how the method behaves when those params are nil.
(3) UINavigationController is a subclass of UIViewController that presents content hierarchically. In this case, the application's window's root view controller is a navigation controller. In turn, that navigation controller's root view controller is your MasterViewController instance.
The documentation for UINavigationController describes it well.