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/// SolidGameObject.h
@interface SolidGameObject : Layer
{
   GameObject *object; // for textures
   b2Body *body;
   b2BodyDef *bodyDef;
   b2CircleShape *shapeDef;
   b2FixtureDef *fixtureDef;
}
- (id)initWithWorld:(b2World *)wrld andCoords:(CGPoint)p;

@property (nonatomic, retain) GameObject *object;
@property (nonatomic, assign) b2Body *body;
@property (nonatomic, assign) b2BodyDef *bodyDef;
@property (nonatomic, assign) b2CircleShape *shapeDef;
@property (nonatomic, assign) b2FixtureDef *fixtureDef;
@end

/// SolidGameObject.mm

#define PTM_RATIO 32
@implementation SolidGameObject
@synthesize object, body, bodyDef, shapeDef, fixtureDef;

- (id)initWithWorld:(b2World *)wrld andCoords:(CGPoint)p
{
   if( (self=[super init]) )
   {
      self.relativeAnchorPoint = NO;
      
      object = [GameObject gameObject];
      [self addChild:object z:1 tag:10];
      
      // THE BODY DEF
      [self setBodyDef:new b2BodyDef];
      [self bodyDef]->isBullet = true;
      [self bodyDef]->fixedRotation = true;
      [self bodyDef]->position.Set(p.x/PTM_RATIO, p.y/PTM_RATIO);
      
      // THE ACTUAL BODY
      body = wrld->CreateBody([self bodyDef]);
      
      // THE CIRCLE SHAPE
      [self setShapeDef:new b2CircleShape];
      [self shapeDef]->m_radius = 3.0f/PTM_RATIO;
      
      // THE FIXTURE
      [self setFixtureDef:new b2FixtureDef];
      [self fixtureDef]->shape = shapeDef;
      [self fixtureDef]->friction = 0.0f;
      [self fixtureDef]->density = 0.0f;
      [self fixtureDef]->restitution = 0.8f;
      
      body->CreateFixture([self fixtureDef]);
      body->SetUserData(object);
   }
   return self;
}
@end

///GameLayer.mm

SolidGameObject *solid = [[[SolidGameObject alloc] initWithWorld:world andCoords:CGPointMake(240,40)] autorelease];
[self addChild:solid z:4 tag:10];