key of CCActionTween

cocos2d-x C++
#1

Is anybody know what is the key parameter means in CCActionTween…

I am trying like this to tween sprite in y direction

cocos2d::CCFiniteTimeAction* rotate = cocos2d::CCActionTween::actionWithDuration(1.0f,“scaleX”,1.0f,1.0f);
sprite>runAction(rotate);

But it is giving error…
I think the parameter “scaleX” is not proper…