Passing FBSDK login manager result between view controllers - ios

Question

I can't transfer the login manager result between view controllers,
The segue is associated to the button and its identifier is s1.
My setup is correct.The program is crashing with green breakpoints.
here is my code:
for the first VC:
import FBSDKLoginKit
class ViewController: UIViewController {
var user_name: String?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
let fbLoginManager = FBSDKLoginManager()
fbLoginManager.logIn(withReadPermissions: ["public_profile", "email"], from: self) { (result, error) in
if let error = error {
print("Failed to login: \(error.localizedDescription)")
return
}
guard let accessToken = FBSDKAccessToken.current() else {
print("Failed to get access token")
return
}
let credential = FIRFacebookAuthProvider.credential(withAccessToken: accessToken.tokenString)
FBSDKGraphRequest(graphPath: "/me", parameters: ["fields" : "email, id, locale"])
.start(completionHandler: { (connection, result, error) in
guard let result = result as? NSDictionary,
let user_name = result["user_name"] as? String,
else {
return
}
if(segue.identifier == "s1"){
if let v = segue.destination as? Re {
v.uname=user_name ?? ""
//v.uname = usr.text ?? ""
}
}
})
// Perform login by calling Firebase APIs
FIRAuth.auth()?.signIn(with: credential, completion: { (user, error) in
if let error = error {
print("Login error: \(error.localizedDescription)")
let alertController = UIAlertController(title: "Login Error", message: error.localizedDescription, preferredStyle: .alert)
return
}
})
}
}
}
And for Re,the next VC:
class Re: UIViewController {
var uname: String?
#IBOutlet weak var l1: UILabel!
var userfb: String?
override func viewDidLoad() {
super.viewDidLoad()
l1.text=uname
// Do any additional setup after loading the view.
}
}

Answer 1

You need to use instance variable which you have declared at top as below.
Now you have create new user_name and use another user_name
guard let result = result as? NSDictionary,
user_name = result["user_name"] as? String,// make change here
else {
return
}