Firebase with Swift 3 counting the number of children

Question

I have an array of strings and I am trying to populate it through firebase. It is a chat application and when a user creates a room he or she names the room. When the user l

Answer 1

Firebase data is loaded (and synchronized) asynchronously. This is easiest to see if you add some debug logging:

let ref = firebase.child("users").child(fUID).child("participating")

print("Starting observing");
ref.observe(.value, with: { (snapshot: FIRDataSnapshot!) in
    print("Got snapshot");
    print(snapshot.childrenCount)
    rooms.count = snapshot.childrenCount
})

print("Returning count");
return rooms.count

When you run this snippet, the logging output will be:

Start observing

Returning count

Got snapshot

This is probably not the order you expected the output to be in. And it also explains why your count will never be correct: the data hasn't been loaded yet, so it can't be counted.

This is the reason why Firebase listeners work with callback blocks: the block is invoked when the data is synchronized.