Cloud function to add/remove the url of a file from Firebase Database that has been added to/removed from Firebase Storage

Question

I'm trying to implement a feature in an app which will list out all the file-names in a ListView and clicking the specific list item will show the contents of the file. I don't really know JavaScript and am also very new to Cloud functions. I wrote a small function which adds metadata to firebase whenever a file is added to firebase storage but it ends up adding the data even when the file is deleted. Here is the code

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

exports.urls = functions.storage.object().onChange( event => {
    const file = event.data;
    const metadata = file.metadata;
    console.log(metadata);
return admin.database().ref("/").set(metadata); });

Can someone please tell me what changes I could make in the above to add urls instead of metadata and also remove the same if the file is being removed?

Answer 1

From the Firebase documentation section Detect resourceState and other event attributes :

The resourceState attribute for an event has the value "exists" (for object creation and updates) or "not_exists" (for object deletion and moves).

 // Exit if this is a move or deletion event. if (resourceState === 'not_exists') { console.log('This is a deletion event.'); return; }