$transaction = Yii::$app->db->beginTransaction();
try{
//删除$model中的数据
$res = $model->deleteAll($cond);
if(!$res)
throw new \Exception('操作失败!');
//删除$model对应的$relation中的数据
$rt = $relation->deleteAll(['polymeric_id'=>$cond['id']]);
if(!$rt)
throw new \Exception('操作失败!');
//以上执行都成功,则对数据库进行实际执行
$transaction->commit();
return Helper::arrayReturn(['status'=>true]);
}catch (\Exception $e){
//如果抛出错误则进入catch,先callback,然后捕获错误,返回错误
$transaction->rollBack();
return Helper::arrayReturn(['status'=>false,'msg'=>$e->getMessage()]);
}