How to display firstname in UILabel?I am developing IOS app with Firebase and Swift - ios

Question

I am practicing IOS app using Firebase and Swift.
This is an basic app where a user logs in with username and password. User can Signup, login, and logout. For this I have created 3 viewcontrollers.One for userlogin, 2nd to signup, and third to display user's firstname and picture.
I have created a viewcontroller "loginPageViewController" to display user's firstname and picture. I am trying to display firstname in "userFirstName" label. But I am unable to do. Error message is attached in screenshot.
Supplements:
Error is occured here
Storyboard
Swift Code:
import UIKit
import Firebase
import FirebaseAuth
class loginPageViewController: ViewController {
#IBOutlet weak var userFirstName: UILabel!
#IBOutlet weak var userImage: UIImageView!
let userID = FIRAuth.auth()?.currentUser?.uid
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
let userID = (FIRAuth.auth()?.currentUser?.uid)!
ref.child("expatsappmembers").child(userID).observeSingleEventOfType(
.Value, withBlock: { (snapshot) in
let firstName = snapshot.value!["firstName"] as! String
self.userFirstName.text = firstName
})
}
#IBAction func LogoutButtoninLoginPage(sender: AnyObject) {
if FIRAuth.auth()?.currentUser != nil{ //there is a user signed in
do{
try FIRAuth.auth()?.signOut()
if FIRAuth.auth()?.currentUser == nil{
let loginVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("InitialView") as? ViewController
self.presentViewController(loginVC!, animated: true, completion: nil)
}
}catch let signOutError as NSError{
print ("Erros signing out: %#", signOutError)
}
}
}
}
"
Any suggestions will be a great help for me.
Thank you in advance.

Answer 1

Before the user have logged in the FIRAuth.auth()?.currentUser?.uid is nil. The problem is that you force unwrap it (!).
You should first check that the user is logged in, and only then continue with your logic.
I would start with this:
if let userID = FIRAuth.auth()?.currentUser?.uid {
ref.child("expatsappmembers").child(userID).observeSingleEventOfType(
.Value, withBlock: { (snapshot) in
if let firstName = snapshot.value?["firstName"] as? String {
self.userFirstName.text = firstName
}
})
}