From: Robert Dober <robert.dober@...>
Date: 2007-06-15T05:35:33+09:00
Subject: Re: is self.var in a class the same as @@var ??

On 6/14/07, Emmanuel Oga <emmanuel@lijasdoblea.com> wrote:
> Is this the same?
>
> class Test
>   @@class_var= ""
> end
>
> class Test
>   self.clas_var= ""
> end
>
> Thanks
>
> --
> Posted via http://www.ruby-forum.com/.
>
>
No it is not, as a matter of fact the second idiom is not correct
(even with the typo corrected)...
irb(main):001:0> class Test
irb(main):002:1>  @@class_var= ""
irb(main):003:1> end
=> ""
irb(main):004:0>
irb(main):005:0* class Test
irb(main):006:1>  self.clas_var= ""
irb(main):007:1> end
NoMethodError: undefined method `clas_var=' for Test:Class
        from (irb):6
        from :0
irb(main):008:0>

...
I believe that you are looking for accessors to class instance
variables, there are no accessors for class variables

class Test
   @a = 42 ### Class instance variable
   @@b = 42 ### Class variable
   class << self
      attr_accessor :a, :b
      def show
        puts  "civar b #{self.b}"
         puts "cvar  b#{@@b}"
      end
  end
end

puts Test.a
puts Test.b
Test.b=1
puts Test.b
Test.show

-------------------
This is a frequent source of confusion at first, so pls keep asking if
I was not very clear :)

HTH
Robert
-- 
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw