observeSingleEvent(of:with:) fetching old data

Question

Background:

I have an app where new users complete a sign-up form (consisting of a username, email, and a password) to register for an account. When the new user submits the form, the app checks its Firebase Database to see if the username has already been taken. The problem here is that observeSingleEvent(of:with:) is not getting the newest data. When I update the data directly from the Firebase console, the changes are not reflected back in the returned results of observeSingleEvent(of:with:). Even between app restarts, the new data changes are not returned.

The only thing I've seen on the issue is here. A user says not to have persistence enabled when using observeSingleEvent(of:with:). But, I have persistence disabled. Also, I set the keepSynced() on the FIRDatabase instance to false (and I've tried true as well). No luck with either setting.

Here's an example of what I am trying:

let usersDatabaseReference = FIRDatabase.database().reference().child("users")
usersDatabaseReference.keepSynced(false)

// Query the database to see if the username is available 
// The user with the username "mark" was removed from the database via the Firebase console
let username = "mark" // This user used to exist in the database (and was previously added through the app).  
usersDatabaseReference.child(username).observeSingleEvent(of: .value, with: { (snapshot) in ... } )

The above code block should return the newest data (one where the user "mark" should not exist).

I am wondering if anyone else ran into this problem, or if anyone has possible solutions.

Note: Developing using iOS 10.1 and swift 3.

Answer 1

the observeSingleEvent(of:with:) return the value only one time

try this :

refHandle = postRef.observe(FIRDataEventType.value, with: { (snapshot) in
  let postDict = snapshot.value as? [String : AnyObject] ?? [:]
  // ...
})

this will add a listener on database event link