swift - Firebase Observe called after following command

Question

I am trying to load a username form a Firebase which is than supposed to be set in an Object. But the Firebase Observe Command is getting called after the name already gets set. What is the problem and how can I fix it?

let ref = Database.database().reference().child("Users").child(currentMessage.senderId).child("name")

ref.observeSingleEvent(of: .value, with: { (snapshot) in

    // This is supposed to be called first
    self.username = snapshot.value as! String
    print(self.username)
})

// This somehow gets called first
let nameModel = NameModel(name: self.username, uid: *some UID*)
decoratedItems.append(DecoratedChatItem(chatItem: nameModel, decorationAttributes: nil))

Answer 1

Waitting for answers