Firebase Queryorderedbychild() Method Not Giving Sorted Data

Firebase queryOrderedByChild() method not giving sorted data

Use method observeEventType instead of observeSingleEventOfType.
Also, make FIRDataEventType to ChildAdded.

Last, If you want Top 20 items, use queryLimitedToFirst instead of queryLimitedToLast.

{
  "users" : {
    "alovelace" : {
      "name" : "Ada Lovelace",
      "score" : 4
    },
    "eclarke" : {
      "name" : "Emily Clarke",
      "score" : 5
    },
    "ghopper" : {
      "name" : "Grace Hopper",
      "score" : 2
    }
  }
}

For the dataset above

let queryRef = FIRDatabase.database().reference().child("users").queryOrderedByChild("score").queryLimitedToFirst(20)
queryRef.observeEventType(.ChildAdded, withBlock: { (snapshot) in
    print("key: \(snapshot.key), value: \(snapshot.value)")
})

key: ghopper, value: Optional({
name = Grace Hopper;
score = 2;
})

key: alovelace, value: Optional({
name = Ada Lovelace;
score = 4;
})

key: eclarke, value: Optional({
name = Emily Clarke;
score = 5;
})

Snapshot will returns the contents as native types.
Data types returned:

• NSDictionary
• NSArray
• NSNumber (also includes booleans)
• NSString

So, you can get your scores this way.

    let queryRef = FIRDatabase.database().reference().child("users").queryOrderedByChild("score").queryLimitedToFirst(20)
queryRef.observeEventType(.ChildAdded, withBlock: { (snapshot) in
    if let scores = snapshot.value as? NSDictionary {
        print(scores["score"])
    }
})

Optional(2)

Optional(4)

Optional(5)

Moreover, the default of realtime database return everything in ascending order.

If you want descending order, you can make some tricks(4:40) in your database.

Sort Firebase Data with queryOrdered by date

I think what you're missing here is the sort function, Please try the code below and let me know what are the results:

DataService.ds.REF_INCOMES.queryOrdered(byChild: "date").observe(.value, with: { (snapshot) in

    guard let usersSnapshot = snapshot.value as? [String:NSObject] else{

        return
    }

    let users = usersSnapshot["users"] as! [String:AnyObject]
    let sorted = users.sorted{($0.0.value["date"] as! Double) > ($0.1.value["date"] as! Double)}

    print(sorted) // It should be: New Year Now, New Year, Last Year
})

How to sort and filter data in Firebase?

It gives you null because it does not exists, you need to do something like this:

queryOrdered(byChild: "TimeStampDateAndTime").queryStarting(atValue: 152).queryEnding(atValue: 152\uf8ff)

this will give you all TimeStampDateAndTime that have 152 at the beginning

Swift - How to create Sort query as Descending on Firebase?

self.posts = self.posts.reverse()

To save NSDate instances, I personally use timeIntervalSinceReferenceDate() which returns an NSTimeInterval (which is a Double), which you can then save in Firebase. When reading the data, you can obtain the original NSDate with init(timeIntervalSinceReferenceDate:).

orderByChild not working in Firebase

When you call snapshot.val(), you are getting back a JSON object. The order of keys in a JSON object is determined by your browser and not by Firebase.

To get the children in order use the built-in forEach method of the snapshot:

self.getAllProfiles = function () {
    var qProfile = $q.defer();
    var ref = new Firebase(FBURL);
    ref.child("users").orderByChild('last_update').on("value", function (snapshot) {
        snapshot.forEach(function(child) {
            console.log(child.val()) // NOW THE CHILDREN PRINT IN ORDER
        });
        qProfile.resolve(snapshot.val());
    }, function (errorObject) {
        qProfile.reject(errorObject);
    });
    return qProfile.promise;
};

You can leave the q.resolve() call where it is: snapshot.forEach() is not an asynchronous call.

Firebase query sort order in swift?

When Firebase loads the data into your tableView data source array, call this:

yourDataArray.sortInPlace({$0.date > $1.date})

Swift 3 Version:

yourDataArray.sort({$0.date > $1.date})

Swift 4 Version:

yourDataArray.sort(by: {$0.date > $1.date})

Request result structure firebasedatabase Swift

In short, if you have extra data at the same level and that makes decodeFirebase crash, you still can use it:

let value = snapshot.value 
let modifiedValue:NSMutableDictionary = (value as AnyObject).mutableCopy() as! MutableDictionary

You then can remove elements by key: modifiedValue.removeObject(forKey: test)
and then apply decode.

How to properly use queryOrderedByValue

When you fire a query against Firebase, it returns the keys of the items that match your query, the value of those items and the relative order of the items in the result. If you listen for a .Value event, all three of these are combined into a single FIRDataSnapshot.

But when you then either ask for the value property of that snapshot or print that snapshot as one block, the data is converted into a Dictionary. Since a dictionary can only contain keys and values, the ordering of the items is lost at that point. And as it turns out, the dictionary then prints the items ordered by their key.

To get the items in order, you should iterate over them using snapshot.children:

leaderboardDB.observeSingleEvent(of: .value, with: { (snapshot) in
    for child in snapshot.children {
        print(child.key)
    }
}, withCancel: nil)

Also see:

• Firebase snapshot.key not returning actual key?
• Firebase getting data in order
• Firebase queryOrderedByChild() method not giving sorted data

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