cocos2d-x C++ singleton

singleton.cpp

#include "GameManager.h"

using namespace cocos2d;

static GameManager *_sharedGameManager = NULL;

GameManager* GameManager::getInstance()
{
    if (! _sharedGameManager)
    {
        _sharedGameManager = new GameManager();
        _sharedGameManager->init();
    }
    
    return _sharedGameManager;
}

GameManager::~GameManager(void)
{
}

bool GameManager::init(void)
{
    return true;
}

singleton.h

#include "cocos2d.h"

class GameManager : public cocos2d::Object
{
    
public:
    /** Returns the shared instance of the Game Manager */
    static GameManager* getInstance(void);

public:
    virtual ~GameManager();
    bool init(void);
};

how can implement destroy _sharedGameManager for clear the vector and take other sprite