From: Philip Mak <pmak@...>
Date: 2002-08-12T01:48:03+09:00
Subject: subclassing and @@variable

I have the following test code:

class XSuperClass
    #@@data = "This is the super class."

    def callme
        puts @@data
    end
end

class XSubClass < XSuperClass
    @@data = "This is the sub class."
end

x = XSubClass.new
x.callme

If I un-comment out the second line and run it, I get this:

This is the sub class.

If I comment out the second line and run it, I get this:

supersub.rb:5:in `callme': uninitialized class variable @@data in XSuperClass (NameError)

Why is the presence of the second line important? The value that it
sets seems to be irrelevant.