Cocos2d-xでシングルトンによる画面間データ連携 ref: http://qiita.com/items/5eca8aab0dbd3f33273c

GameManager.cpp

//
//  GameManager.cpp
//  SingletonTEST
//
//  Created by prototechno on 2013/02/20.
//
//
#include "SimpleAudioEngine.h"
#include "GameManager.h"

using namespace cocos2d;
using namespace CocosDenshion;

//All static variables need to be defined in the .cpp file
//I've added this following line to fix the problem
GameManager* GameManager::m_mySingleton = NULL;

GameManager::GameManager()
{

}

GameManager* GameManager::sharedGameManager()
{
    //If the singleton has no instance yet, create one
    if(NULL == m_mySingleton)
    {
        //Create an instance to the singleton
        m_mySingleton = new GameManager();
    }

    //Return the singleton object
    return m_mySingleton;
}

GameManager.h

//
//  GameManager.h
//  SingletonTEST
//
//  Created by prototechno on 2013/02/20.
//
//

#ifndef __SingletonTEST__GameManager__
#define __SingletonTEST__GameManager__

typedef enum{
    GameModeMenu ,
    GameModeNagasa ,
    GameModeKasa ,
}GameMode;

#include "cocos2d.h"

class GameManager
{
private:
    GameManager();
    static GameManager* m_mySingleton;

public:
    static GameManager* sharedGameManager();

    GameMode gameMode;

    int count;

    float gameTime;

};

#endif /* defined(__SingletonTEST__GameManager__) */

sample.cpp

#include "GameManager.h"

void Play5::countTimer(float time)
{
    GameManager::sharedGameManager()->gameTime += time;

    //時間を表示する
    CCString* timeString = CCString::createWithFormat("%8.0f秒", GameManager::sharedGameManager()->gameTime);
    CCLabelTTF* timerLabel = (CCLabelTTF*)this->getChildByTag(kTagTimerLabel);
    timerLabel->setString(timeString->getCString());
}