code: function() {
          return !!this.getFields().findBy(function(field) {
              var preventMark = field.preventMark,
                  isValid;
              field.preventMark = true;
              isValid = field.isValid();
              field.preventMark = preventMark;
              return !isValid;
          });
      }
docs: Returns true if the form contains any invalid fields. No fields will be marked as invalid
  as a result of calling this; to trigger marking of fields use {@link #isValid} instead.