Question: So suppose I have this (not working): 

```
class User
   description = "I am User class variable"
   def print
       puts description
   end
end

```

So, how should I use the var description, how to pass this into a method as a default parameter, or used in the method directly? Thanks..

Answer: 
You can access the class-scope using `define_method`.

```
class User
   description = "I am User class variable"
   define_method :print do
       puts description
   end
end

```

> 
> > User.new.print  
> 
>  I am User class variable  
> 
>  => nil
> 
> 
> 

I don't think it's good idea, though :)
To define a class variable, use an `@@`:

```
class User
   @@description = "I am a User class variable"

   def print
       puts @@description
   end
end

```