怎么没返回 $this

// 按类目筛选商品
public function category(Category $category)\
{\
  if ($category->is_directory) {\
  $this->params['body']['query']['bool']['filter'][] = [\
  'prefix' => ['category_path' => $category->path.$category->id.'-'],\
  ];\
  } else {\
  $this->params['body']['query']['bool']['filter'][] = ['term' => ['category_id' => $category->id]];\
  }\
}