一个节点创建另一个对象,如何调用这个对象里的脚本方法

怎么才能调用到ball这个script里的方法

     var ball = this._scene.getChildByName("ball");
     console.log(ball); 
     ballAction = ball.getComponent("Ball");
     ballAction.ballMove();

log显示object
但是之后就报错了
Simulator: JS Exception: assignment to undeclared variable ballAction, file: /Users/michael/Desktop/Learn/temp/quick-scripts/assets/HeroControl.js, lineno: 257

assignment to undeclared variable ballAction…

你 ballAction 没有声明啊…