def valid_attribute?(attribute)
    case attr_type_for(attribute)
    when :bool
      validate_class_for(attribute, [TrueClass, FalseClass])
    when :datetime, :datetimecombo
      validate_class_for(attribute, [DateTime])
    when :int
      validate_class_for(attribute, [Fixnum, Float])
    else 
      if @attributes[attribute].blank?
        add_error(attribute, "cannot be blank")
      end
    end
  end
def valid_attribute?(attribute)
    case attr_type_for(attribute)
    when :bool
      validate_class_for(attribute, [TrueClass, FalseClass])
    when :datetime, :datetimecombo
      validate_class_for(attribute, [DateTime])
    when :int
      validate_class_for(attribute, [Fixnum, Float])
    else 
      if @attributes[attribute].blank?
        add_error(attribute, "cannot be blank")
      end
    end
  end
TODO: Add test cases for validations