CODEWITHSUNDEEP
javascriptnode.jsfirebasefirebase-realtime-database
Matt D. Webb
Matt D. Webb

Reputation: 3314

Firebase orderByChild unexpected results

I have the follow single child data structure and want to retrieve an order list by child property rating:

sample data structure

players: {
    360368: {
        name: "Joe, Blogs",
        rating: 1853
    },
    400017: {
        name: "Bob, Dylan",
        rating: 2597,
    },
    430013: {
        name: "James, Dean",
        rating: 2152,
    }
}

Retrieval code

let ref = this.fb.ref('players');

ref.orderByChild("rating").limitToFirst(100).once("value", function(snapshot) {
     console.log(snapshot.val());
});

The results returned appear to have no logical numeric order.

Finally, when I run the following query I get the results I expect (seeing ten players with a rating 2597):

let ref = this.fb.ref('players');

ref.orderByChild("rating").equal(2597).limitToFirst(10).once("value", function(snapshot) {
     console.log(snapshot.val());
});

UPDATE

It appears that the data is being returned by object key. How can I ensure this is returned, ordered by rating?!

Upvotes: 1

Views: 754

Answers (1)

Frank van Puffelen
Frank van Puffelen

Reputation: 598740

When you request a value event for a query, Firebase returns a snapshot that contains all children and information on their order. But when you request the val() of that snapshot, the children are converted into a JOSN object and the ordering information is lost.

The solution is to use the snapshot to navigate the children and only convert to JSON once you've gotten them in the right order:

let ref = this.fb.ref('players');

ref.orderByChild("rating").equal(2597).limitToFirst(10).once("value", function(snapshot) {
    snapshot.forEach(function(childSnapshot) {
        console.log(childSnapshot.val());
    });
});

Upvotes: 6

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