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.

Solution 1

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.

Solution 2

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 };
    });
});

Comments

[Nalaka526]

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]

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]

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

[Nalaka526]

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

[alex kucksdorf]

Glad to help! ;)

[gamengineers]

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

[Laker]

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

[J4GD33P 51NGH]

I'm using timestamp as orderBy and its showing latest added at last. It should show first

[pesho hristov]

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