public function categoryAdd(Request $request)
 {
     $name = $request->input('name', '');
     $category_no = $request->input('category_no', '');
     $parent_id = $request->input('parent_id', '');
     $preview = $request->input('preview', '');
     $category = new Category();
     $category->name = $name;
     $category->category_no = $category_no;
     $category->preview = $preview;
     if ($parent_id != '') {
         $category->parent_id = $parent_id;
     }
     $category->save();
     $m3_result = new M3Result();
     $m3_result->status = 0;
     $m3_result->message = '添加成功';
     return $m3_result->toJson();
 }