How to use Firebase Database to update in-app URLs in real time.

Update: So I have my Firebase real-time database populated with some data, and I have already integrated Firebase within my app, and the database's structure looks like this:

myDatabase
.
.
. . . Child/node
.
.
.
. . . Child with value of "url"

How do I reference and read the value (the URL) from the database so that the following code uses that URL to open the SFSafariViewController?

Here is the code I use to open the SFSafariViewController using a button tap:

Code Block @IBAction func openSFWebView(_ sender: Any) {
        guard let url = URL(string: "https://www.google.com") 
            else {return}
        let safariViewController = SFSafariViewController (url: url)
        self.present(safariViewController, animated: true, completion: nil)
    }

From what I could find online, it seems like I should use observeSingleEventType, but I do not want to have to/don't believe I need to authenticate the user or use the user's ID to access the URL.

Below is from the Firebase documentation:
let newID = Auth.auth().currentUser?.uid (I don't believe I need this.)
ref.child("childName").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
  // Get user value
  let value = snapshot.value as? NSDictionary
  let username = value?["username"] as? String ?? ""
  let user = User(username: username)

  // ...
  }) { (error) in
    print(error.localizedDescription)
}

Again, I hope someone can help.

Thank You!