Firebase queryOrderedbyChild doesn't return a Null value

Question

I have a query that searches for users based on their age:

self?.ref.child(\"users\").queryOrdered(byChild: \"age\").queryStarting(atValue: \"18\").queryEnding(a         


        

Answer 1

In the data you show there are no nodes with 19 or higher, so the query doesn't match any nodes. In that case the .childAdded event does not fire.

If you want to detect this condition, you must listen to the .value event, which does fire even when there are no children. But you'll get a single .value event for all matching children in this case, so you'll need to loop over the child nodes:

self?.ref.child("users")
  .queryOrdered(byChild: "age").queryStarting(atValue: "18")
  .queryEnding(atValue: "25")
  .observeSingleEvent(of: .value, with:  { (snapshot) in
    print(snapshot.exists())
    for child in snapshot.children {
      ...
    }