ios-登录和注册按钮不工作（树屋和解析）

Question

我的登录和注册按钮工作但由于某些原因我填写了unsername和密码字段 - 并按下登录按钮 - 按钮不会推送到我的收件箱控制器。但是，如果我停止我的项目，然后重新运行它，它将加载登录。我不知道为什么！任何帮助将不胜感激 -

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
self.navigationItem.hidesBackButton = YES;
}


- (IBAction)login:(id)sender {


NSString *username = [self.usernameField.text
                      stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

NSString *password = [self.passwordField.text
                      stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

if ([username length] == 0 || [password length] == 0) {
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Oops!"
                                                        message:@"Make sure you enter a username and password!"
                                                       delegate:Nil cancelButtonTitle:@"Okey"
                                              otherButtonTitles:nil];
    [alertView show];
} else {
    [PFUser logInWithUsernameInBackground:username password:password block:^(PFUser *user, NSError *error) {
        if (error) {
            UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Sorry!"
                                                                message:[error.userInfo objectForKey:@"error"]
                                                               delegate:Nil cancelButtonTitle:@"Ok"
                                                      otherButtonTitles:nil];
            [alertView show];
        } else {
            [self.navigationController popToRootViewControllerAnimated:YES];
        }
    }];
}
}

@end