cocos2d中关于回调函数的pSender参数的问题

运行结果显示，CallBack1和CallBack2产生的效果是一样的，请问CallBack2处的pSender的作用是什么，为什么Sprite* sp = (Sprite*)pSender;后sp与sprite等效了？

cpp中

 void MyScene::goMenu(cocos2d::Ref* pSender)
{
    log("Tag=%i",this->getTag());
    switch (this->getTag())
    {
    case func:
        this->OnCallFunc(pSender);
        break;
    case funcN:
        this->OnCallFuncN(pSender);
        break;

    }
}
void MyScene::backMenu(Ref* pSender)
{
    Scene* scene = HelloWorld::createScene();
    Director::getInstance()->replaceScene(scene);
}

void MyScene::OnCallFunc(Ref* pSender)
{
    FiniteTimeAction* ac1 = MoveBy::create(2,Vec2(100,100));
    FiniteTimeAction* ac2 = ac1->reverse();
    FiniteTimeAction* acf = CallFunc::create(CC_CALLBACK_0(MyScene::CallBack1,this));
    FiniteTimeAction* seq = Sequence::create(ac1,acf,ac2,NULL);
    log("%p", this->sprite);
    this->sprite->runAction(Sequence::create(seq,NULL));
}
void MyScene::OnCallFuncN(Ref* pSender)
{
    FiniteTimeAction* ac1 = MoveBy::create(2, Vec2(100, 100));
    FiniteTimeAction* ac2 = ac1->reverse();
    FiniteTimeAction* acf = CallFuncN::create(CC_CALLBACK_1(MyScene::CallBack2, this));
    FiniteTimeAction* seq = Sequence::create(ac1, acf, ac2, NULL);
    sprite->runAction(Sequence::create(seq,NULL));
}

void MyScene::CallBack1()
{
    sprite->runAction(TintBy::create(0.5, 255, 0, 255));

}
void MyScene::CallBack2(Ref* pSender)
{
    Sprite* sp = (Sprite*)pSender;
    sp->runAction(TintBy::create(0.5, 255, 0, 255));
}

头文件中

 #pragma once
#include "cocos2d.h"

using namespace cocos2d;

class MyScene :public Layer
{
    Sprite* sprite;
public:
    static Scene* createScene();
    virtual bool init();
    CREATE_FUNC(MyScene);

    void goMenu(Ref* pSender);
    void backMenu(Ref* pSender);

    void OnCallFunc(Ref* pSender);
    void OnCallFuncN(Ref* pSender);

    void CallBack1();
    void CallBack2(Ref* pSender);
};

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