Getting id of the current user from Cloud Functions and Firebase

Question

I am using google cloud functions to register push notifications through firebase. In my app, i have a notifications reference that changes for a current user whenever they get a new follower or like, etc. As of right now I am able to send the notification to the phone whenever that whole reference child changes

For example, if any single post is liked, then it will send a notification. What I need to do is observe the current user to only send the notification that single person.

Here is my JavaScript file

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
exports.sendPushNotification = functions.database.ref('/notification/{id}').onWrite(event => {
const payload = {
notification: {
    title: 'New message arrived',
    body: 'come check it',
    badge: '1',
    sound: 'default',
}
  };

  return admin.database().ref('fcmToken').once('value').then(allToken => {
    if (allToken.val()) {
        const token = Object.keys(allToken.val());
        return admin.messaging().sendToDevice(token, payload).then(response => {

        });
    }
  });

});

I would like to replace this line:

functions.database.ref('/notification/{id}').onWrite(event => {

With this:

functions.database.ref('/notification/{id}').(The current user ID).onWrite(event => {

How do I get the current users id?

Answer 1

You seem very new to JavaScript (calling it JSON is sort-of a give-away for that). Cloud Functions for Firebase is not the best way to learn JavaScript. I recommend first reading the Firebase documentation for Web developers and/or taking the Firebase codelab for Web developer. They cover many basic JavaScript, Web and Firebase interactions. After those you'll be much better equipped to write code for Cloud Functions too.

Now back to your question: there is no concept of a "current user" in Cloud Functions. Your JavaScript code runs on a server, and all users can trigger the code by writing to the database.

You can figure out what user triggered the function, but that too isn't what you want here. The user who triggered the notification is not the one who needs to receive the message. What you want instead is to read the user who is the target of the notification.

One way to do this is to read it from the database path that triggered the function. If you keep the notifications per user in the database like this:

user_notifications
  $uid
    notification1: ...
    notification2: ...

You can trigger the Cloud Function like this:

exports.sendPushNotification = functions.database.ref('/user_notification/{uid}/{id}').onWrite(event => {

And then in the code of that function, get the UID of the user with:

var uid = event.params.uid;

Answer 2

For Swift 3.0 - 4.0

You can do this:

import Firebase
import FirebaseAuth


class YourClass {

let user = Auth.auth().currentUser
let userID = user.uid

// user userID anywhere 

}