@IBOutlet weak var emailField: UITextField!
@IBOutlet weak var passwordField: UITextField!
var UserUid: String!

override func viewDidLoad() {
    super.viewDidLoad()
  **strong text**}

@IBAction func SignIn (_ sender: AnyObject) {

 if let email = emailField.text, let password = passwordField.text {
        Auth.auth().signIn(withEmail: email, password: password, completion: { (user, error) in
        if error == nil {

            self.UserUid = user?.user.uid

            KeychainWrapper.standard.set(self.UserUid, forKey: "uid")}


            self.performSegue(withIdentifier: "toMessages", sender: nil)}

            else {

            self.peformSegue(withIdentifier: "toSignUp", sender: nil)