相关疑难解决方法(0)

我试图在用户成功登录到他们的帐户后切换视图控制器,但它无法正常工作.我不能直接使用segue,因为如果单击登录按钮,它将转到该视图控制器,无论信息是否正确.我已经尝试了所有我知道但没有成功的事情.这是我正在尝试的代码.

   @IBAction func loginTapped(sender: AnyObject) {

    let username = usernameField.text
    let password = passwordField.text

    if username.isEmpty || password.isEmpty {
        var emptyFieldsError:UIAlertView = UIAlertView(title: "Please try again", message: "Please fill in all the fields we can get you logged in to your account.", delegate: self, cancelButtonTitle: "Try again")
        emptyFieldsError.show()
    }

    PFUser.logInWithUsernameInBackground(username, password:password) {
        (user: PFUser?, error: NSError?) -> Void in
        if user != nil {
            self.performSegueWithIdentifier("Klikur", sender: self)
        } else {
            if let errorString = error!.userInfo?["error"] as? String {
                self.errorMessage = …