There only ever is one `RadioGroup` class and classes in Ruby are objects :-) It's an instance variable on the class side, not on the object side. It's a bit weird, let me showcase: 

```
tobi@speedy:~$ irb
2.0.0p195 :001 > class A
2.0.0p195 :002?>   @i = 1
2.0.0p195 :003?>   def self.i
2.0.0p195 :004?>     @i
2.0.0p195 :005?>     end
2.0.0p195 :006?>   attr_reader :i
2.0.0p195 :007?>   def initialize(i)
2.0.0p195 :008?>     @i = i
2.0.0p195 :009?>     end
2.0.0p195 :010?>   end
 => nil 
2.0.0p195 :011 > A.i
 => 1 
2.0.0p195 :012 > b = A.new 'a'
 => #<A:0x000000026a3590 @i="a"> 
2.0.0p195 :013 > b.i
 => "a" 
2.0.0p195 :014 > A.i
 => 1 
2.0.0p195 :015 > 
```

I think there is a way to get to the app, don't have it in  my head right now though. The easies would be to pass it in on radio/radiogroup creation as they are created from the app.