fix

src/factory/Elm.php

@@ -86,7 +86,7 @@ abstract class Elm
      *
      * @return Popover
      */
-    public static function poptip()
+    public static function popover()
     {
         return new Popover();
     }

src/rule/BaseRule.php

@@ -242,11 +242,13 @@ trait BaseRule
     protected function parseBaseRule()
     {
         $rule = [
-            'value' => $this->value,
-            'field' => $this->field,
             'type' => $this->type
         ];
 
+        if (!is_null($this->field))
+            $rule['field'] = $this->field;
+        if (!is_null($this->value))
+            $rule['value'] = $this->value;
         if (!is_null($this->title))
             $rule['title'] = $this->title;
         if (!is_null($this->className))