how to update a value in firebase realtime database using Cloud Functions for Firebase

Question

I went though the firebase docs for updating a value in realtime database using Cloud Functions for Firebase, but am not able to understand.

My database structure is

{   
 "user" : {
    "-KdD1f0ecmVXHZ3H3abZ" : {
      "email" : "[email protected]",
      "first_name" : "John",
      "last_name" : "Smith",
      "isVerified" : false
    },
    "-KdG4iHEYjInv7ljBhgG" : {
      "email" : "[email protected]",
      "first_name" : "Max1",
      "last_name" : "Rosse13131313l",
      "isVerified" : false
    },
    "-KdGAZ8Ws6weXWo0essF" : {
      "email" : "[email protected]",
      "first_name" : "Max1",
      "last_name" : "Rosse13131313l",
      "isVerified" : false
    } 
}

I want to update the isVerified using database trigger cloud functions. I don't know how to update a database value using cloud functions (language : Node.JS)

I wrote a code to automatically update the value of the key 'isVerified' of a user, when the user is created by using database trigger onWrite. My code is

const functions = require('firebase-functions');

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

exports.userVerification = functions.database.ref('/users/{pushId}')
    .onWrite(event => {
    // Grab the current value of what was written to the Realtime Database.
    var eventSnapshot = event.data;

    if (event.data.previous.exists()) {
        return;
    }

    eventSnapshot.update({
        "isVerified": true
    });
});

but when i deploy the code, and add a user to the database, the cloud function log shows the below error

TypeError: eventSnapshot.child(...).update is not a function
    at exports.userVerification.functions.database.ref.onWrite.event (/user_code/index.js:10:36)
    at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:35:20
    at process._tickDomainCallback (internal/process/next_tick.js:129:7)

The Cloud Functions documentation has a section and a set of examples for this. Where specifically are you stuck? — Frank van Puffelen
I am not able to understand the example give in the docs, i need help in understanding the same or someother example code to study with. Thank you in advance. — Thooyavan Manivaasakar
It is unlikely that somebody will just come up with a better example than what is in the documentation. Instead of asking for that, show what you've already tried and where you got stuck. — Frank van Puffelen
Hi, i have updated the post with the details of what i tried and the error that i got. Kindly for addressing it, my mistake, i should have given details first itself. Kindly help me out. — Thooyavan Manivaasakar
@ThooyavanManivaasakar I'm having nearly same problem , I want to update a field in Users/{UserID}/(this field) when new user is created . I tried these solutions but nothing worked for me .Would you like to help me ? — xaif

Doug Stevenson Doug Stevenson · Accepted Answer · 2017-04-18T17:16:25

You are trying to call update() on a DeltaSnapshot object. There is no such method on that type of object.

var eventSnapshot = event.data;
eventSnapshot.update({
    "isVerified": true
});

event.data is a DeltaSnapshot. If you want to change the data at the location of the change represented by this object. Use its ref property to get a hold of a Reference object:

var ref = event.data.ref;
ref.update({
    "isVerified": true
});

Also, if you are reading or writing the database in a function, you should always return a Promise that indicates when the change is complete:

return ref.update({
    "isVerified": true
});

I would recommend taking Frank's advice from the comments and study the existing sample code and documentation to better understand how Cloud Functions works.

how to update a value in firebase realtime database using Cloud Functions for Firebase

1 Answers