Newb: How to separate files/classes (chipmunk)

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Newb: How to separate files/classes (chipmunk)

(6 posts) (4 voices)

Started 2 years ago by vennt
Latest reply from vennt

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vennt
Member

I'm learning Cocos and Chipmunk mostly through examples. Now trying to branch out a little bit. But I'm stuck.

Not sure if I'm even doing this correctly - but I've got 1 scene that I'm trying to initialize chipmunk:

TestScene.m

-(void) initChipmunk
{
	// Start chipmunk
	cpInitChipmunk();
	space = cpSpaceNew();
	space->gravity = cpv(0, -100);
}

I've got another class with my sprite that I'm trying to add to this scene with chipmunk

MyBox.m

-(id) init
{
	if((self = [super init]))
	{
		Sprite *mySprite = [Sprite spriteWithFile:@"Icon.png"];
		CGSize s = [[Director sharedDirector] winSize];
		mySprite.position = ccp(s.width /2, s.height/2);
		[self addChild:mySprite z:0];

		body = cpBodyNew(100.0, INFINITY);
		body->p = cpv(s.width /2, s.height/2);
		cpSpaceAddBody(space, body);

		shape = cpCircleShapeNew(body, 20.0, cpvzero);
		shape->e = 0.5; // Elasticity
		shape->u = 0.8; // Friction
		shape->data = mySprite;
		shape->collision_type = 1;
		cpSpaceAddShape(space, shape);
	}
	return self;
}

My issue is I do not know how to call these files from my TestScene.m init: Right now I'm doing something like this.

TestScene.m

-(id) init
{
	if((self = [super init]))
	{
		[self initChipmunk];

		MySprite *icon = [MySprite node];
		[self addChild:icon];

		[self schedule: @selector(step:)];
	}
	return self;
}

I'm getting a build error in MyBox.m "error: 'space' undeclared (first use in function)"

I guess my chipmunk space is not present in the file, because its initialized in my scene file.

I'm not really sure if I'm going about this correctly, every demo/tutorial I've done has always added the chipmunk initialization, body creation, shape creation in one long block, I was looking to sorta compartmentalize some of that...

Posted 2 years ago #

XyrisKenn
Member
I'm up against the same issue but with Box2D. This is what I've found but don't completely understand yet.
I think it's just a basic Obj-C/C++ technique of integrating class files with the main game implementation, but I come from actionscripting which is different.

The solution seems to do with making the main game scene accessible to the class files and calling the 'world' through a nested function.

Looking at Luke's example UIKit app at http://blog.zincroe.com/2009/05/iphone-and-box2d/ he builds classes for 'Ball' and 'Obstacle', but connects to the main class through an Actor class. I looked for a key Box2D function in 'Ball.m' and found:

[self setBody:[[self game] world]->CreateBody([self bodyDef])];

'game' is defined in the 'Actor' class files:
```
Actor.h: 	MyGameViewController *game;
Actor.m: @synthesize game;
```
...and his main scene is defined as a class:

@class MyGameViewController; // which is where the main game logic is.

Ball class is called in the main game scene (MyGameViewController) as:
```
MyGameViewController.h: @class Actor;
MyGameViewController.m: #import "Actor.h"
```
...then in a function as
Ball *aBall = [[[Ball alloc] init] autorelease];

...so it seems 'Ball' and 'Obstacle' (Actor) classes in his example can access the physic's Box2D world.
I'm sorting through Luke's work and not my own, I suggest asking him.
Posted 2 years ago #
jd
Member

@vennt put cpSpace *space; in your .h file.

Posted 2 years ago #
vennt
Member

@XyrisKenn thanks for the examples - I'm probably not really understanding it due to it being Box2d though, if I can't get this working maybe I'll start using Box2d...

@jd thanks for the tip, putting the cpSpace *space in the MyBox.h file gets rid of my build error. but now the simulator is crashing once the cocos2d splash screen appears.

FWIW, I've got the code successfully running if I put everything in one continuous block, but kind of defeats the purpose here ;)

Posted 2 years ago #
Mark Sawicki
Member
@vennt,

Maybe you could either pass in the chipmunk space to your MySprite init , or don't try to add the shape and body to the space in the init of your object, but instead do it in your MainScene code, like:
```
MySprite *icon = [MySprite node];
		cpSpaceAddBody(space, [icon body]);
		cpSpaceAddShape(space, [icon shape]);
		[self addChild:icon];
```
Posted 2 years ago #
vennt
Member
@Mark

Thanks a bunch! Everything seems to be working.

I ended up modifying my init method to take the space.
```
initWithCPSpace:(cpSpace*)space
```
So now I'm doing this
```
[self initChipmunk];

MySprite *icon = [[MySprite node] initWithCPSpace:space];
[self addChild:icon];
```
Although I'm not sure if thats best practice, I think your second method sounds a bit better.
Posted 2 years ago #

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