From: Stefano Crocco <stefano.crocco@...>
Date: 2008-06-10T15:11:40+09:00
Subject: Re: accessing class variables from the outside (beginner question)

On Tuesday 10 June 2008, progcat@comcast.net wrote:
> I am still learning Ruby and   I am trying to get something
> like this to work and am unsure how.
>
> I know I could do attr_reader to
> access "ones" but ones might be an
> array, hash, etc.
>
> Is there a way to do something like this:
> class Test
>    def initialize
>      @try["hashworld"] = 10000
>      @ones = 1,2,3,4
>    end
>    def addit(one,two)
>       #can code add one + two, from
>       #inside and outside?
>       return(one + two)
>    end
> end
> tens = 10,20,30,40,50
> a = Test.new
> p a.addit(ones[1],tens[0]) #prints 12
> p a.addit(tens[3],ones[0]) #prints 41
> p a.addit(tens[3],try["hashworld"]) #prints 10040
>
> Thanks,
> Tom

As first thing, variables like @try and @ones in your code are not class 
variables, as the subject of your post implies, but instance variables. Class 
variables are something else (their names start with @@, are shared among the 
class object itself, its instances, derived class objects and their 
instances).

Regarding your question. The only way to access instance variables from 
outside the instance is to create accessor methods for them. You can do it 
using attr_reader and similar, or you can write them by hand. For example:

class Test
  ...

  def ones
    @ones
  end

end

I hope this helps

Stefano