改进自关联查询多级调用问题

library/think/Model.php

@@ -192,7 +192,7 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
         $con = Db::connect($connection);
         // 设置当前模型 确保查询返回模型对象
         $queryClass = $this->query ?: $con->getConfig('query');
-        $query      = new $queryClass($con, $this->class);
+        $query      = new $queryClass($con, $this);
 
         // 设置当前数据表和模型名
         if (!empty($this->table)) {
@@ -208,6 +208,19 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
         return $query;
     }
 
+    /**
+     * 创建新的模型实例
+     * @access public
+     * @param  array|object $data 数据
+     * @param  bool         $isUpdate 是否为更新
+     * @param  mixed        $where 更新条件
+     * @return Model
+     */
+    public function newInstance($data = [], $isUpdate = false, $where = null)
+    {
+        return (new static($data))->isUpdate($isUpdate, $where);
+    }
+
     /**
      * 获取当前模型的查询对象
      * @access public
@@ -599,7 +612,7 @@ abstract class Model implements \JsonSerializable, \ArrayAccess
      */
     protected function getRelationData(Relation $modelRelation)
     {
-        if ($this->parent && get_class($this->parent) == $modelRelation->getModel()) {
+        if ($this->parent && $modelRelation->getModel() == $this->parent) {
             $value = $this->parent;
         } else {
             // 首先获取关联数据