From: stern@... (Alan Stern)
Date: 2002-02-11T02:29:00+09:00
Subject: Class variable madness

Can someone tell me what's going on here?  Or has this already been fixed?


a.rb(main):001:0> RUBY_VERSION
"1.6.5"
a.rb(main):002:0> RUBY_PLATFORM
"i586-linux"
a.rb(main):003:0> RUBY_RELEASE_DATE
"2001-09-19"
a.rb(main):004:0> 
a.rb(main):005:0* class A
a.rb(main):006:1> #	@@v = 0
a.rb(main):007:1* 	def A.set(x)
a.rb(main):008:2> 		@@v = x
a.rb(main):009:2> 	end
a.rb(main):010:1> 	def A.get
a.rb(main):011:2> 		@@v
a.rb(main):012:2> 	end
a.rb(main):013:1> 	def set(x)
a.rb(main):014:2> 		@@v = x
a.rb(main):015:2> 	end
a.rb(main):016:1> 	def get
a.rb(main):017:2> 		@@v
a.rb(main):018:2> 	end
a.rb(main):019:1> end
nil
a.rb(main):020:0> 
a.rb(main):021:0* class B < A
a.rb(main):022:1> 	@@v = 0
a.rb(main):023:1> end
0
a.rb(main):024:0> 
a.rb(main):025:0* a = A.new
#<A:0x401e6c48>
a.rb(main):026:0> b = B.new
#<B:0x401e4e98>
a.rb(main):027:0> 
a.rb(main):028:0* A.set(3)
NameError: uninitialized class variable @@v in A
	from a.rb:8:in `set'
	from a.rb:28

		# Why didn't that work?

a.rb(main):029:0> A.get
NameError: uninitialized class variable @@v in A
	from a.rb:11:in `get'
	from a.rb:29
a.rb(main):030:0> B.get
0
a.rb(main):031:0> b.get
NameError: uninitialized class variable @@v in A
	from a.rb:17:in `get'
	from a.rb:31

		# How come b.get and B.get are trying to access
		# different class variables?

a.rb(main):032:0> 
a.rb(main):033:0* a.set(5)
5
a.rb(main):034:0> A.set(5)
5

		# Why did this work now when it didn't work before?

a.rb(main):035:0> A.get
5
a.rb(main):036:0> B.get
0
a.rb(main):037:0> b.get
5