use the sof attributes for equality

lib/virtual/object.rb

@@ -7,9 +7,17 @@ module Virtual
   class Object
     def == other
       return false unless other.class == self.class 
-      attributes.each do |a|
-        left = send(a)
-        right = other.send(a)
+      Sof::Util.attributes(self).each do |a|
+        begin
+          left = send(a)
+        rescue NoMethodError
+          next  # not using instance variables that are not defined as attr_readers for equality
+        end
+        begin
+          right = other.send(a)
+        rescue NoMethodError
+          return false
+        end
         return false unless left.class == right.class 
         return false unless left == right
       end