How to create a Cloud Function and triggering it in Cloud Firestore

Question

I am new to Cloud Firestore , I want to create a function when a new user has been been added to Firestore, it generates a unique random number and save it in a document. How I can achieve it using Google Cloud Console?

Answer 1

You can achieve this, by simply pressing the ADD COLLECTION button which looks like this:

A new pop-up will come up, which looks like this:

Name your collection in every way you want. I have named it Products. Press NEXT and a new pop-up will come up again:

Leave the Document id field blank. Choose a filed (I named id productName) and a value of type String named Milk.

This is the result:

You can use Cloud Functions for Firebase, so every time a new entry (document) is added on a specific location in your Cloud Firebase database, you'll be able to trigger another frunction. For that, I'll give you an example. Let's assume we want to send a notification to a user when something happens.

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.yourFunction = functions.firestore.document("notifications/{uid}/userNotifications/{notificationId}").onWrite(event => {
    const uid = event.params.uid;
    const notificationId = event.params.notificationId;

    return admin.firestore().collection("notifications").doc(uid).collection("userNotifications").doc(notificationId).get().then(queryResult => {
        const uid = queryResult.data().senderUid;
        const notificationMessage = queryResult.data().notificationMessage;

        const fromUser = admin.firestore().collection("users").doc(senderUid).get();
        const toUser = admin.firestore().collection("users").doc(uid).get();

        return Promise.all([fromUser, toUser]).then(result => {
            const fromUserName = result[0].data().userName;
            const toUserName = result[1].data().userName;
            const tokenId = result[1].data().tokenId;

            const notificationContent = {
                notification: {
                    title: "Your Title",
                    body: notificationMessage,
                    icon: "default",
                    sound : "default"
                }
            };

            return admin.messaging().sendToDevice(tokenId, notificationContent).then(result => {
                console.log("Notification sent!");
            });
        });
    });
});

So when a new write operation is taking place as this path notifications/{uid}/userNotifications/{notificationId}, whith other words a new document appears we can create a Promise and send a notification.