CCLayer update method with box2d bodies failure

Question

I'm reading the book:'Learning Cocos2D' from Rod Strougo and Ray Wenderlich and I decided to make my own iOS game with Cocos2d-Box2d. Now I have a problem that I can not resolve. I created a class called Box2dLayer, which inherits from CCLayer and I have Level1Layer class that inherits from Box2dLayer. Everything worked fine until I had two different type of box2d bodies to render on the screen. Now every time I start the game it fails at -[Box2DLayer update:] method giving the following: Thread 1: EXC_BAD_ACCESS(code=1, address= 0xsomething); 1 - [Box2DLayer update:] at line sp.position... 2 - [CCScheduler update:] at line entry->impMethod( entry->target, updateSelector, dt );

And Here is my code:

//Box2DSprite.h
@interface Box2DSprite : CCSprite
{
    b2Body *body;
}
@property (assign) b2Body *body;
@end

//Box2DSprite.mm

@implementation Box2DSprite
@synthesize body;
-(void)dealloc
{

    body = NULL;
    [super dealloc];
}
@end

//Box2DLayer.h
@interface Box2DLayer : CCLayer
{
    b2World *world;
    GLESDebugDraw *debugDraw;
    b2MouseJoint *mouseJoint;
    b2Body *groundBody;
}
-(void)setupGround;
@end

//Box2DLayer.mm

@implementation Box2DLayer
-(id)init
{
    if (self = [super init]) {
        [self scheduleUpdate];
        [self setupWorld];
        [self setupDebugDraw];
        [self setupGround];
        self.isTouchEnabled = YES;
    }
    return self;
}

- (void)setupWorld {
    b2Vec2 gravity = b2Vec2(0.0f, -10.0f);
    world = new b2World(gravity);
    //world->SetContinuousPhysics(true);
}

-(void) draw {    
    ccGLEnableVertexAttribs( kCCVertexAttribFlag_Position );
    kmGLPushMatrix();
    world->DrawDebugData();
    kmGLPopMatrix();
}

- (void)setupDebugDraw {
    debugDraw = new GLESDebugDraw(PTM_RATIO *[[CCDirector sharedDirector] contentScaleFactor]);
    world->SetDebugDraw(debugDraw);
    debugDraw->SetFlags(b2Draw::e_shapeBit);
}
- (void)registerWithTouchDispatcher {
    [[[CCDirectorIOS sharedDirector] touchDispatcher]  addTargetedDelegate:self priority:0
                                                           swallowsTouches:YES];
}
-(void)update:(ccTime)dt {
    int32 velocityIterations = 3;
    int32 positionIterations = 2;
    world->Step(dt, velocityIterations, positionIterations);
    for(b2Body *b = world->GetBodyList(); b != NULL; b = b->GetNext())
    {
        if (b->GetUserData() != NULL) {
            Box2DSprite *sp = (Box2DSprite *) b->GetUserData();
            sp.position = ccp(b->GetPosition().x * PTM_RATIO*RETSIZE,b->GetPosition().y * PTM_RATIO*RETSIZE);
            sp.rotation = CC_RADIANS_TO_DEGREES(b->GetAngle() * -1);
        }
    }
}
-(void)setupGround{
    CGSize winSize = [[CCDirector sharedDirector] winSize];
    b2BodyDef groundBodyDef;

    groundBodyDef.type = b2_staticBody;
    groundBodyDef.position.Set(0, 10/RETSIZE/PTM_RATIO);
    groundBody = world->CreateBody(&groundBodyDef);
    CCSprite *gsprite = [CCSprite spriteWithFile:@"ground.png"];
    groundBody->SetUserData(gsprite);

    b2EdgeShape groundBox;

    groundBox.Set(b2Vec2(0,0), b2Vec2(winSize.width/PTM_RATIO/RETSIZE-150/PTM_RATIO,0));
    groundBody->CreateFixture(&groundBox,0);

}
-(BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event{
    CGPoint touchLocation = [touch locationInView:[touch view]];
    touchLocation = [[CCDirector sharedDirector] convertToGL:touchLocation];
    touchLocation = [self convertToNodeSpace:touchLocation];

    b2Vec2 locationWorld = b2Vec2(touchLocation.x/PTM_RATIO/RETSIZE, touchLocation.y/PTM_RATIO/RETSIZE);

    b2AABB aabb;
    b2Vec2 delta = b2Vec2(1.0/PTM_RATIO/RETSIZE, 1.0/PTM_RATIO/RETSIZE);
    aabb.lowerBound = locationWorld - delta;
    aabb.upperBound = locationWorld + delta;
    SimpleQueryCallback callback(locationWorld);
    world->QueryAABB(&callback, aabb);

    if (callback.fixtureFound) {
        b2Body *body = callback.fixtureFound->GetBody();

        b2MouseJointDef joint;
        joint.bodyA = groundBody;
        joint.bodyB = body;
        joint.target = locationWorld;
        joint.maxForce = 100*body->GetMass();
        joint.collideConnected = true;

        mouseJoint = (b2MouseJoint *)world->CreateJoint(&joint);
       // body->SetAwake(false);
        return YES;
    }

}

-(void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event{
    CGPoint touchLocation = [touch locationInView:[touch view]];
    touchLocation = [[CCDirector sharedDirector]
                     convertToGL:touchLocation];
    touchLocation = [self convertToNodeSpace:touchLocation];
    b2Vec2 locationWorld = b2Vec2(touchLocation.x/PTM_RATIO/RETSIZE, touchLocation.y/PTM_RATIO/RETSIZE);
    if (mouseJoint) {
        mouseJoint->SetTarget(locationWorld);        
    }

}

-(void)ccTouchEnded:(UITouch *)touch withEvent:(UIEvent *)event{
    if (mouseJoint) {
        world->DestroyJoint(mouseJoint);
        mouseJoint = NULL;
        }
}
-(void) dealloc
{
    if (world) {
        delete world;
        world = NULL;

    }
    if (debugDraw) {
        delete debugDraw;
        debugDraw = NULL;
    }
    [super dealloc];
}
@end

The program crashes at the for loop inside the update method.NOTE that if I comment out the for loop , everything works , but the sprites aren't attached to the box2D bodies.

If you can not give the answer , what is wrong, tell me please a list of possible problems. Thanks!

Siby Siby · Accepted Answer · 2013-01-06T20:26:21

Hi the error says it is a memory issue; You are trying to access some thing that is not there. 2 things; In your code I dont see anywhere the sprite bodies being attached to the world. second, why is the body property in Box2dSprite class assign, shouldn't it be retain.

CCLayer update method with box2d bodies failure

2 Answers