How to filter Firebase data in Swift?

Question

Basically, I have a structure called, topics which contains Title, Description and a Published flag (see screenshot below for clarific

Answer 1

self.ref = FIRDatabase.database().referenceFromURL(FIREBASE_URL).child("topics").
    queryOrderedByChild("published").queryEqualToValue(true)
    .observeEventType(.Value, withBlock: { (snapshot) in
    for childSnapshot in snapshot.children {
        print(snapshot)
    }
})