/**
  * 编辑版块
  * @param $id
  */
 public function update($id)
 {
     try {
         $model = new BoardModel();
         $board = $model->find($id);
         if (empty($board)) {
             throw new Exception('版块不存在');
         }
         if (IS_POST) {
             $model->post($_POST, $id);
             $this->redirect('index');
         } else {
             $this->assign('board', $board);
             $this->assign('pageTitle', '编辑版块');
             $this->display('post');
         }
     } catch (Exception $e) {
         $this->error($e->getMessage());
     }
 }