CCNode，CCSprite是如何实现绘制的？

Node类的draw是空函数，没有真正描画，Node中有下面的解释
A Node is a "void" object. If you want todraw something on the screen, you should use a Sprite instead. Or subclass Nodeand override `draw`.
由此可见，真正的描画是在node的子类中，draw函数有以下注释，说明设置opengl的状态
/**
* Override this method to draw your ownnode.
* The following GL states will be enabledby default:
* -`glEnableClientState(GL_VERTEX_ARRAY);`
* - `glEnableClientState(GL_COLOR_ARRAY);`
* -`glEnableClientState(GL_TEXTURE_COORD_ARRAY);`
* - `glEnable(GL_TEXTURE_2D);`
* AND YOU SHOULD NOT DISABLE THEM AFTERDRAWING YOUR NODE
* But if you enable any other GL state,you should disable it after drawing your node.
*/
再看sprite类的draw函数中有
renderer->addCommand(&_quadCommand);
由此可见真正的描画是在sprite类中做的，再往下涉及到opengl的机制了，到此为止吧。