obj.ancestors =>祖先链
祖先链的构造:
ruby寻找方法的步骤
从祖先链最底处开始寻找,找到方法后,若方法里面还有嵌套方法,则需要重新在祖先链底端找起
从外部来看,寻找步骤是从下到上,但”寻找探针”进入个体之后,则寻找步骤是从上到下.上溯是按照就近原则(in case there are some methods that are overridden,Ruby is intended to use the new ones),下溯是按照定义先后(it what is defined first would be considered first)(very logically)私有方法服从一个简单的规则:不能明确指定一个接收者来调用一个私有方法