Class variables and instance variables in ruby

First, in ruby1.8, class variables are shared by all sub-classes and parent classes.Code:

Class intelligentlife @ home_planet = nil def self. home_planet @ home_planet end def self. home_planet = (x) @ home_planet = x end #... end class Terran
We can see that the results are the same, all of which are "Mars". This is because the class variables of the parent class are shared by the entire inheritance system.
Here, if we want to get the results we need, we need to use class instance variables (note,Class instance variablesIs placed outside the method,Instance variablesOtherwise, because the class instance variables are strictly per-class, rather than shared by the entire inheritance system.
Class intelligentlife @ home_planet = nil class