Firestore : Retrieve a single document

Question

I want to retrieve a single document from Firestore. So I do not mean the list of documents in the collection (I know how to do that). Let's say I know one of the key-value pair of the document and I would like to find and retrieve the document into Angular 4.

Answer 1

Use flatmap to return the single document data:

First import the .flatMap() property.

import { AngularFirestore } from 'angularfire2/firestore';
import 'rxjs/add/operator/mergeMap';

Then query your collection and limit it to 1 document:

this.afs.collection('collection', ref => ref.where('value', '==', true) 
.limit(1)).valueChanges().flatMap(result => result);

Then you can subscribe to that and it will return the flatened json instead of an array.

EDIT:

And you can just do like this to use it in your html directly:

this.userInfo = this.afs.collection('collection', ref => ref.where('value', 
'==', true).limit(1)).valueChanges().flatMap(result => result);

In the html code:

<p>{{ (userInfo | async)?.duration }}</p>