Send push notifications using Cloud Functions for Firebase

Question

I am trying to make a cloud function that sends a push notification to a given user.

The user makes some changes and the data is added/updated under a node in firebase database (The node represents an user id). Here i want to trigger a function that sends a push notification to the user.

I have the following structure for the users in DB.

Users   - UID  - - email  - - token   - UID  - - email  - - token 

Until now i have this function:

exports.sendNewTripNotification = functions.database.ref('/{uid}/shared_trips/').onWrite(event=>{ const uuid = event.params.uid;  console.log('User to send notification', uuid);  var ref = admin.database().ref('Users/{uuid}'); ref.on("value", function(snapshot){         console.log("Val = " + snapshot.val());         },     function (errorObject) {         console.log("The read failed: " + errorObject.code); }); 

When i get the callback, the snapshot.val() returns null. Any idea how to solve this? And maybe how to send the push notification afterwards?

Answer 1

I managed to make this work. Here is the code that sends a notification using Cloud Functions that worked for me.

exports.sendNewTripNotification = functions.database.ref('/{uid}/shared_trips/').onWrite(event=>{     const uuid = event.params.uid;      console.log('User to send notification', uuid);      var ref = admin.database().ref(`Users/${uuid}/token`);     return ref.once("value", function(snapshot){          const payload = {               notification: {                   title: 'You have been invited to a trip.',                   body: 'Tap here to check it out!'               }          };           admin.messaging().sendToDevice(snapshot.val(), payload)      }, function (errorObject) {         console.log("The read failed: " + errorObject.code);     }); }) 

Answer 2

Just answering the question from Jerin A Mathews... Send message using Topics:

const functions = require('firebase-functions'); const admin = require('firebase-admin');  admin.initializeApp(functions.config().firebase);  //Now we're going to create a function that listens to when a 'Notifications' node changes and send a notificcation //to all devices subscribed to a topic  exports.sendNotification = functions.database.ref("Notifications/{uid}") .onWrite(event => {     //This will be the notification model that we push to firebase     var request = event.data.val();      var payload = {         data:{           username: request.username,           imageUrl: request.imageUrl,           email: request.email,           uid: request.uid,           text: request.text         }     };      //The topic variable can be anything from a username, to a uid     //I find this approach much better than using the refresh token     //as you can subscribe to someone's phone number, username, or some other unique identifier     //to communicate between      //Now let's move onto the code, but before that, let's push this to firebase      admin.messaging().sendToTopic(request.topic, payload)     .then((response) => {         console.log("Successfully sent message: ", response);         return true;     })     .catch((error) => {         console.log("Error sending message: ", error);         return false;     }) }) //And this is it for building notifications to multiple devices from or to one.