Using AngularFirestore Collection orderBy with snapShotChanges method

Question

I have below code in an Angular application which is using AngularFire2.

TypeScript:

constructor(db: AngularFirestore) {
    this.booksCollectionRef = db.collection<Book>('books');

    this.books = this.booksCollectionRef.snapshotChanges().map(actions => {
        return actions.map(action => {
            const data = action.payload.doc.data() as Book;
            const id = action.payload.doc.id;
            return { id, ...data };
        });
    });
}

HTML:

<md-list>
    <md-list-item *ngFor="let book of books | async">
        <h4 md-line>{{book.name}}</h4>
    </md-list-item>
</md-list>

This code retrieves and binds data as expected (removes items when collection updated), now I want to sort the collection by a given column. I tried to use firebase orderBy clause, but I can not figure out how to use it with snapShotChanges() method.

Have you tried: this.books = this.booksCollectionRef.orderBy('name','desc').snapshotChanges().map(actions => — Gal Bracha
– Gal Bracha, Commented Oct 8, 2017 at 12:38
@GalBracha that also does not work. Property 'orderBy' does not exist on type 'AngularFirestoreCollection<Book>' — Nalaka526
– Nalaka526, Commented Oct 8, 2017 at 15:37
Have you tried the default sort() function of TypeScript ? If not then please provide us with the structure of your this.books. — M0nst3R
– M0nst3R, Commented Oct 10, 2017 at 16:52
@GhassenLouhaichi, Not yet. That would be my last option.But I'm trying to get this done within 'snapshotChanges()' because I may need to use some other functions in firestore collection, similarly. — Nalaka526
– Nalaka526, Commented Oct 10, 2017 at 16:59
I am not following, if you are using .map after your snapshotChanges() call, can't you simply follow that by a .sort call to sort your results ? — M0nst3R
– M0nst3R, Commented Oct 10, 2017 at 17:01

alex kucksdorf · Accepted Answer · 2017-10-11 10:56:03Z

64

+50

The following should work for your use case:

this.booksCollectionRef = db.collection<Book>('books', ref => ref.orderBy('order field'));

Take a look at the documentation of AngularFirestore for further information on this topic.

answered Oct 11, 2017 at 10:56

alex kucksdorf

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6 Comments

Nalaka526 Over a year ago

But I can not find a way to use ref.orderBy method with snapShotChanges method, Can you please show me a sample code...

alex kucksdorf Over a year ago

It should be working if you just replace the first line in your constructor with the one I posted. Check out the example app at the bottom of the page I linked, they use this approach in combination with valueChanges()

alex kucksdorf Over a year ago

Did you change orderBy(‘order field‘) to the correct field of your books you want to order by?

Nalaka526 Over a year ago

I'm so sorry... I tried this again and it works.. Previous day I've missed something... Thanks a lot :)

alex kucksdorf Over a year ago

Glad to help! ;)

|

OroshiX · Accepted Answer · 2018-02-12 15:43:27Z

11

this.announcementCollectionRef = afs.collection<Announcement>('announcements', ref => ref.orderBy('createdAt', 'desc'));
this.announcements = this.announcementCollectionRef.snapshotChanges().map(actions => {
    return actions.map(a => {
        const data = a.payload.doc.data() as AnnouncementId;
        const id = a.payload.doc.id;
        return { id, ...data };
    });
});

edited Feb 12, 2018 at 15:43

OroshiX

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answered Oct 14, 2017 at 3:00

Clayton Allen

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2 Comments

gamengineers Over a year ago

life saver. This code worked for me w/ ionic, angular2fire, and firestore.

pesho hristov Over a year ago

How is this supposed to work when you don't subscribe to the DocumentChangeAction observer?

sgt_lagrange · Accepted Answer · 2017-10-11 17:09:11Z

0

Not sure about Angular Fire, but you can try using the Firebase Firestore libraries directly.

The following code works for me:

someCollectionRef
.orderBy('columnName')
.onSnapshot((snapshot) => {
snapshot.docChanges.forEach(function (change) {
...doStuff

answered Oct 11, 2017 at 17:09

sgt_lagrange

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1 Comment

Laker Over a year ago

Do you know why it says to me "Property 'forEach' does not exist on type '(options?: SnapshotListenOptions) => DocumentChange[]'." please?

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