iOS compiling order - ios

Question

It is one of my first days at iOS programming. I came from C++ and have specific silly question. How does compiler work and go through the code?
How I understand all starts with public interface, then continues to private. How implementation works? Methods? Is view controller as main function in C++ and it goes through all methods at the start?
Here is my viewController .h and .m. This program already has some other classes and action buttons. Maybe someone can explain step-by-step. Thanks.
ViewController.h
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#interface ViewController : UIViewController
#end
ViewController.m
#import "ViewController.h"
#import "Deck.h"
#import "PlayingCardDeck.h"
#interface ViewController ()
#property (weak, nonatomic) IBOutlet UILabel *flipsLabel;
#property (nonatomic) int flipCount;
#property (strong, nonatomic) Deck *deck;
#end
#implementation ViewController
- (Deck *)lol
{
if (!_deck) _deck = [self createDeck];
return _deck;
}
- (Deck *)createDeck
{
return [[PlayingCardDeck alloc] init];
}
- (void)setFlipCount:(int)flipCount{
_flipCount=flipCount;
_flipsLabel.text = [NSString stringWithFormat:#"Count: %d", _flipCount];
NSLog(#"%d", self.flipCount);
}
- (IBAction)touchCardButton:(UIButton *)sender {
if ([sender.currentTitle length]) {
[sender setBackgroundImage:[UIImage imageNamed:#"cardback"] forState:UIControlStateNormal];
[sender setTitle:#"" forState:UIControlStateNormal];
}
else {
Card *randomCard = [self.lol drawRandomCard];
if (randomCard){
[sender setBackgroundImage:[UIImage imageNamed:#"cardfront"] forState:(UIControlStateNormal)];
[sender setTitle:randomCard.contents forState:UIControlStateNormal];
self.flipCount++;
}
}
}
#end

Answer 1

The beginning of the program code is similar to c++, it is the very c main() function.
Within your main the framework is called (by instaticating an UIApplication or subclass object) and the names of the application class and the application delegate class are handed over to the framework. The cocoa touch framework will then instantiate the application first and instantiate the delegate and assign the delegate to the application.
Typcially the first method from your program code that is invoked is the UIApplicationDelegate method application:willFinishLaunchingWithOptions: but the one that you typcially start with is application:didFinishLaunchingWithOptions:
There some preparation is set up, which is often not required especially when you work with a storyboard or when you set the main interface in your project properties. According to these properties or storyboard one view controller is the root view controller that is invoked first. For the view controllers it is quite similar. You would use NIB files or storyboards in most cases to define their UI Items and then viewDidLoad is the first method that is being invoked with regard to the root view.
Given your code you are likely to add something like this:
-(void) viewDidLoad {
[super viewDidLoad];
[self createDeck]
// here you may want to access some UIView objects in order to display your deck.
}

Answer 2

I don't know if you understand how c++ compiles, Objective-C is all the same.
First preprocessor translate all preprocess code(#import, #macro, etc), and then every .m file is considered a compile unit, they are compile separately in to object files without a specific order.
Then linker links all object files together.
If you don't understand what compile unit or object file are, I suggest you do more research on how preprocessor, compiler, linker works, since it is a too broad topic to explain here.