iOS - Firebase Filter query

Question

I got score node in Firebase:

And under score node my data structure is as:

{
"jjTO29ziQ2SjrH5PFzY7ZMpSgjq1-Kak6FCyGtdy_kcEPd4K" =     {
    jjTO29ziQ2SjrH5PFzY7ZMpSgjq1 = "-Kak6FCyGtdy_kcEPd4K";
    score = 5;
};
"jjTO29ziQ2SjrH5PFzY7ZMpSgjq1-KbE_pgfUsukOm4uW0bx" =     {
    jjTO29ziQ2SjrH5PFzY7ZMpSgjq1 = "-KbE_pgfUsukOm4uW0bx";
    score = 4;
};

Question: Can I filter the data by score ?

I tried doing :

FIRDatabase.database().reference().child("scores").queryOrdered(byChild: "score").observeSingleEvent(of: .value, with: { (snapshot) in

        debugPrint(snapshot.value ?? "nil")

    })

But can't get the result ?

You Can filter by data with orderByChild but I think your problem is because you haven entered the corresponding nodes that have score inside. Because you are entering score at the beginning as a child, but first you need to enter to each of your id`s. — Mago Nicolas Palacios, Jan 25 '17 at 11:50
@MagoNicolasPalacios : I have my node set up as in picture 1 ? Can you suggest any ? — user3804063, Jan 25 '17 at 11:53
@FrankvanPuffelen: yeah debug print is called but the data is not sorted by score — user3804063, Jan 25 '17 at 11:56
But did you get what I say? You are entering scores and then filtering by score, and scores doesn't have a direct child named score, it has 2 different childs that inside of them there is a value called score. — Mago Nicolas Palacios, Jan 25 '17 at 12:03
@MagoNicolasPalacios: yep you are right I got no direct child named score. I have to filter . Can I achieve this ? — user3804063, Jan 25 '17 at 12:06
You can! I think the answer below is correct. (Frank van Puffelen) — Mago Nicolas Palacios, Jan 25 '17 at 12:08

score 6 · Answer 1 · answered Jan 25 '17 at 12:03

When you execute a query against Firebase, you get a FIRDataSnapshot that contains three pieces of information for each result:

its key
its value
its position relative to other nodes

When you're calling snapshot.value the snapshot is converted into a Dictionary. Unfortunately that dictionary can only hold key-value pairs, so you lose the information on the position of the nodes. So while the data in the snapshot is actually sorted correctly, you're throwing that information away.

The solution is to use the FIRDataSnapshots built-in children property to loop over the child nodes in the correct order. The Firebase documentation on querying has this sample of how to do that:

_commentsRef.observeEventType(.Value, withBlock: { snapshot in
  for child in snapshot.children {
    ...
  }
})

iOS - Firebase Filter query

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