我有一个导航视图控制器，它在动作时向标签栏视图控制器发送一个序列。由于这个序列，标签栏视图控制器继承了导航栏。我试图将一个标题应用到标签栏视图控制器上的一个视图控制器上，但是通过代码设置标题对我不起作用。有人知道这是为什么吗？
下面是我的故事板图片：

带有注销按钮的视图控制器是我试图在导航栏中设置标题的地方（代码）：

import UIKit

class ProfileSettingsViewController: UIViewController {

    override func viewWillAppear(animated: Bool) {

        self.navigationItem.title = "Profile Settings"

    }

    override func viewDidLoad() {
        super.viewDidLoad()

        self.navigationItem.leftBarButtonItem = nil

    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    @IBAction func logoutButton(sender: AnyObject) {

        PFUser.logOut()
        var currentUser = PFUser.currentUser()
        self.performSegueWithIdentifier("userLoggedOut", sender: self)
        self.navigationController?.setNavigationBarHidden(self.navigationController?.navigationBarHidden == false, animated: true)

    }

}

视图控制器嵌入在导航控制器中，触发选项卡栏控制器的继续：

import UIKit

class UserRegistrationViewController: UIViewController {

    func displayAlert(title:String, error:String) {

        var alert = UIAlertController(title: title, message: error, preferredStyle: UIAlertControllerStyle.Alert)

        alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: {
            action in


        }))

        self.presentViewController(alert, animated: true, completion: nil)

    }

    @IBOutlet var usernameTextField: UITextField!

    @IBOutlet var emailTextField: UITextField!

    @IBOutlet var passwordTextField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func registerUser(sender: AnyObject) {

        var error = ""

        if usernameTextField.text == nil || emailTextField.text == nil || passwordTextField.text == nil {

            error = "Please enter a username, email and password"

        }

        if error != "" {

            displayAlert("Error In Form", error: error)

        } else {

            var user = PFUser.currentUser()

            user.username = usernameTextField.text
            user.password = passwordTextField.text
            user.email = emailTextField.text

            user.saveInBackgroundWithBlock {
                (succeeded: Bool!, signupError: NSError!) -> Void in
                if signupError == nil {

                    println(user.username)
                    println(user.password)
                    println(user.email)

                    self.performSegueWithIdentifier("successfulRegistration", sender: self)

                    self.navigationController?.setNavigationBarHidden(self.navigationController?.navigationBarHidden == false, animated: true)

                    // Hooray! Let them use the app now.
                } else {

                    if let errorString = signupError.userInfo?["error"] as? NSString {
                        error = errorString
                    } else {

                        error = "Please try again later."

                    }

                    self.displayAlert("Could Not Sign Up", error: error)

                }
            }

        }

    }


}