Gets data from the Firestore Database along with the query

Question

I only need to download data from the Firestore Database that is equal to something. It crashes me an error:

Cannot read property 'onSnapshot' of undefined

How can I get data from Firestore and create a query?

My code:

const messages = this.firestore.collection('chat', ref => {
    ref.where('receiver_id', '==', employee.user.id);
    }).valueChanges().subscribe((message) => {
        console.log(message);
    });

My Firestore Database:

Answer 1

You're not returning anything from within the callback, which means that AngularFire ends up trying to call onSnapshot on undefined.

It should be either:

const messages = this.firestore.collection('chat', ref => {
    return ref.where('receiver_id', '==', employee.user.id);
}).valueChanges().subscribe((message) => {
    console.log(message);
});

Or more commonly written as:

const messages = this.firestore.collection('chat', ref => ref.where('receiver_id', '==', employee.user.id))
.valueChanges().subscribe((message) => {
    console.log(message);
});