set value of user rating to Firebase Database - ios

Question

I try to send the voting from users to firebase and save them under the specific user.
class User: NSObject {
var id: String?
init(dictionary: [String: AnyObject]) {
self.id = dictionary["id"] as? String
}
var ref: DatabaseReference!
var numberOfGood = 0
init(id: String? = nil) {
self.id = id
ref = Database.database().reference().child("users").childByAutoId()
}
init(snapshot: DataSnapshot){
ref = snapshot.ref
if let value = snapshot.value as? [String : Any] {
numberOfGood = value["numberOfGood"] as! Int
}
}
func save() {
let postDictionary = [
"id" : self.id,
"numberOfGood" : self.numberOfGood,
] as [String : Any]
self.ref.setValue(postDictionary)
}
}
Inside the viewController where to vote I handle the voting itself like this:
class UserRatingClass {
var numberOfGood = 0
var ref = Database.database().reference().child("users").childByAutoId()
func good() {
numberOfGood += 1
ref.child("numberOfGood").setValue(numberOfGood)
}
}
var userRating: UserRatingClass! {
didSet {
let x = userRating.numberOfGood
self.good.setTitle("\(x) 👍", for: [])
}
}
#IBAction func goodReview(_ sender: UIButton) {
userRating.good()
let x = userRating.numberOfGood
self.good.setTitle("\(x) 👍", for: [])
}
I tried different ways like
var StringGood = String(user?.numberOfGood)
self.ref.child("users").child(StringGood).setValue(x)
inside the buttonActionFunction but by this I'm always getting Cannot invoke initializer for type 'String' with an argument list of type '(Int?)' as an error...
Edit: I call the User.swift class like this:
var user: User?