segue设置好了却报has no segue with identifier

新手。。
写了个登陆微博的小demo，获取token后打算跳转到别的页面，

- (void)sinaweiboDidLogIn:(SinaWeibo *)sinaweibo
{
    [self saveWeiboInfo];

    NSLog(@"uid= %@ accessToken= %@", sinaweibo.userID, sinaweibo.accessToken);

    [self performSegueWithIdentifier:@"login" sender:self];

}

获得token后报错：

2013-02-18 17:31:50.683 WeiboTimeline[5690:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Receiver (<WeiboLoginViewController: 0x712a850>) has no segue with identifier 'login''

segue的identifier已经设置好了

但是。。在viewdidLoad里，很奇怪的却能跳转

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSDictionary *dic = [[NSUserDefaults standardUserDefaults] dictionaryForKey:@"weiboUserData"];
    NSString *token = [dic valueForKey:@"access_token"];
    NSLog(@"token= %@", token);
    if (token != nil) {
        [self performSegueWithIdentifier:@"login" sender:self];
    }
}

上面这样，token获取了保存后，下次再打开应用就能跳转。。

明明是一样的代码。。为什么上面那个报错。。。求解

http://blog.csdn.net/liangguo03/article/details/7956163

你参考一下这个调试的文章