元のメッセージを編集して、コードをそのまま含めました。ご迷惑をおかけして申し訳ありません。
これは、プロジェクトに追加したクラスへのポインターを使用しようとしている場所です。
#ifndef MYAPP_DivGameLayer_h
#define MYAPP_DivGameLayer_h
// When you import this file, you import all the cocos2d classes
#include "cocos2d.h"
#include "Box2D.h"
#include "DivBall.h"    
#define PTM_RATIO 32
#define GRAVITY -10.0f
#define VELOCITY_ITERS 8
#define POSITION_ITERS 1
#define BALLS_COUNT 2
class DivGameLayer : public cocos2d::CCLayer {
public:
    ~DivGameLayer();
    DivGameLayer();
    // returns a Scene that contains the layer as the only child
    static cocos2d::CCScene* scene();
    // functions for handling user input touches    
    virtual void ccTouchesEnded(cocos2d::CCSet* touches, cocos2d::CCEvent* event);
    // game update loop function
    void update(float dt);
private:
    // CONSTANTS
    float SCREEN_WIDTH;
    float SCREEN_HEIGHT;
    b2World* world;                 // the game's world
    DivBall* balls;                 // balls
    int next;                       // pointer to next ball
    // initialize the game's world
    void initWorld();
    // initialize balls
    void initBalls();
};
#endif
これは私のDivBallヘッダーファイルです:
#ifndef MYAPP_DivBall_h
#define MYAPP_DivBall_h
#include "DivGameLayer.h"
#define PATH "ball.png"
#define DENSITY 0.25f
#define FRICTION 0.1f
#define RESTITUTION 0.7f
class DivBall : public cocos2d::CCSprite {
public:
    ~DivBall();
    DivBall(DivGameLayer layer, b2World* world, cocos2d::CCPoint location, float Vx, float Vy, float omega);
private:
    DivBall();    
    b2Body* body;
};
#endif
これはDivBall.cppです:
#include "DivBall.h"
#include "SimpleAudioEngine.h"
using namespace cocos2d;
using namespace CocosDenshion;
// defualt CTOR
DivBall::DivBall()
{
}
// CTOR
DivBall::DivBall(DivGameLayer layer, b2World* world, CCPoint location, float Vx, float Vy, float omega)
{
    CCSprite *sprite = CCSprite::create(PATH);
    sprite->setPosition( CCPointMake(location.x, location.y) );
    layer->addChild(sprite);
    // Define the dynamic body.
    b2BodyDef bodyDef;
    bodyDef.type = b2_dynamicBody;
    bodyDef.position.Set(location.x/PTM_RATIO, location.y/PTM_RATIO);
    bodyDef.userData = sprite;
    b2Body *body = world->CreateBody(&bodyDef);
    // Define a circle shape for our dynamic body.
    b2CircleShape circle;
    circle.m_radius = (sprite->getContentSize().width/2.0f)/PTM_RATIO;
    // Define the dynamic body fixture.
    b2FixtureDef fixtureDef;
    fixtureDef.shape = &circle;
    fixtureDef.density =  DENSITY;
    fixtureDef.friction = FRICTION;
    fixtureDef.restitution = RESTITUTION;
    body->CreateFixture(&fixtureDef);
    // set velocity
    body->SetLinearVelocity(b2Vec2(Vx/PTM_RATIO, Vy/PTM_RATIO));
    body->SetAngularVelocity(omega);
}
// DCTOR
DivBall::~DivBall()
{
        // nothing...
}
GameLayerでコンパイルエラーが発生します:不明なタイプ名Ball。
はっきりしないのでごめんなさい。