Creating class objects objective c - objective-c

Question

I started transferring my java knowlege into objective c quite recently and got into making apps with xcode too. I do have a few things I'm confused about though. First of all in java when I'm making top down games and need to shoot a projectile, I would do that somewhat like:
public class Bullet{
int x,y;
public bullet(double x, double y){
this.x = x;
this.y = y;
}
public void tick(){
//logic goes in here to move bullet
}
}
then I'd have a class with an arraylist:
public class MainClass{
ArrayList<Bullet> bulletlist;
public main(){
//create an arraylist that takes Bullet objects
bulletlist = new ArrayList<Bullet>();
//add a new bullet at the coordinate (100,100)
bulletlist.add(new Bullet(100,100));
}
//gameloop(we'll pretend that this gets called every millisecond or so)
public void gameloop(){
//loop through list
for(int i = 0; i < bulletlist.size(); i++){
//run the method tick() at the current index
bulletlist.get(i).tick();
}
}
}
so... my question is how would I translate this code into objective c. Or in other terms, how do I create an arraylist similar to the one in the example that creates an object of a class , then finally loop through this and call a loop method or whatever method I create inside.

Answer 1

Objective-C has no generics, unlike Java. It wouldn't make much sense, since Objective-C is dynamically typed (for the most part). Instead, NSMutableArray and NSArray store instances of NSObject or subtypes thereof (similar to ArrayList<Object> in Java).
Something like this should get you started.
#interface MainClass()
#property(nonatomic, strong) NSMutableArray *bullets;
#end
#implementation MainClass
- (id)init {
if (self = [super init]) {
self.bullets = [NSMutableArray array];
[self.bullets addObject:[[Bullet alloc] initAtX:100 y:100]];
}
return self;
}
- (void)gameLoop {
[self.bullets makeObjectsPerformSelector:#selector(tick)];
}
#end

Answer 2

you create a new file inherited by NSObject with xcode, declare your header and your body, and your ArrayList<Bullet> can be a simple NSMutableArray. Your loop can look like this
NSMutableArray *bulletlist = [[NSMutableArray alloc] init];
// fill the array
for(Bullet *bullet in bulletlist) // or a simple for loop
{
[bullet tick];
}
for steps how to create and declera a class, just check some apple tutorials :)

Answer 3

Your "main class" should be a UIViewController. It should create a UIView which is full screen on the phone. Then it adds a "CALayer" object as a sublayer of that view's layer.
There are various ways to draw into a CALayer, the best in this case would be to create a "BulletLayer" subclass of CALayer and do your drawing in that.
A view is a rectangle of the screen that the user can see and touch. A layer is a set of pixels stored in the video card's [very fast] memory that can be manipulated by your code. For best performance you will only draw the pixels once, and then move them around the screen (which can be done with animation, etc).
If you want specific answers about any particular part of that, you should ask a new question for each after checking if it's already answered somewhere.

Answer 4

It would look like this:
// bullet.h
#interface Bullet : NSObject
#property(assign, nonatomic) CGPoint position;
- (id)initWithPosition:(CGPoint)position;
#end
// bullet.m
#implementation Bullet
- (id)initWithPosition:(CGPoint)position {
self = [self init];
if (self) {
_position = position;
}
return self;
}
#end
Then, in some other class that uses bullets (like a view controller), declare an array to keep the bullets...
#import "Bullet.h"
// put this in the class's interface
#property(nonatomic, strong) NSMutableArray *bullets;
... and add a new bullet like this:
[self.bullets addObject:[[Bullet alloc] initWithPosition:CGPointMake(100,100}];
... and iterate bullets like this:
for (Bullet *bullet in self.bullets) {
NSLog(#"bullet position is %#", NSStringFromCGPoint(bullet.position));
}