convertToWorldSpace无效

原因：只能是sprite的父节点来调用convertToWorldSpace

Sprite A-->SpriteB

if you want know the position of your spriteB in the current worldyou must call the "convertToWorldSpace" methods from its parent(the spriteA) :

[spriteA convertToWorldSpace:spriteB.position];

The "convertToWorldSpace:" method applies the node's transformationto the given position.You should always callthis methods from the parent's sprite.