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[QUOTE="Jeremy Henty, post: 4503581"]
Is this really the whole story?  Because until now I always thought I
didn't understand class variables but if this is so then now I do.
Wheeeee!

But there's at least one gotcha; a class variable shadows any class
variable of the same name that you subsequently create in an ancestor
class:

$ irb
irb(main):001:0> class A ; end ; class B < A ; end
=> nil
irb(main):002:0> class B ; @@x = 1 ; end ; class A ; @@x = 0 ; end
=> 0
irb(main):003:0> class A ; puts @@x ; end ; class B ; puts @@x ; end
0
1
=> nil
irb(main):004:0> exit

.... but if you create the class variable in the ancestor class first
then the descendant class inherits it instead of creating a new one:

$ irb
irb(main):001:0> class A ; end ; class B < A ; end
=> nil
irb(main):002:0> class A ; @@x = 0 ; end ; class B ; @@x = 1 ; end
=> 1
irb(main):003:0> class A ; puts @@x ; end ; class B ; puts @@x ; end
1
1
=> nil
irb(main):004:0> exit

Any other subtleties?

Cheers,

Jeremy Henty
[/QUOTE]

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