Can't access data base from a Firebase function - firebase

Question

I tried everything , I have this cloud function (that otherwise works) :
exports.contentServer = functions.https.onRequest((request, response) => {
admin.database().ref('/list/' + "abc").once('value').then(function(snapshot) {
console.log(snapshot.val() );
return null;
}).catch(function(error) {
console.log("Error getting document:", error);
return response.send(error);
});
});
or also this :
admin.database().ref('/list').once('value').then(function(snapshot) {
var event = snapshot.val();
app.tell('Result: '+event);
});
and this :
exports.contentServer = functions.https.onRequest((request, response) => {
var db = admin.database();
db.ref("list/abc").once("value").then(snap => {
var store = snap.val().description;
return store;
}).then(() => {
var store = snap.val().description;
return store;
}).then(snap => {
var store = snap.val().description;
return store;
}).catch(err => {
console.log(err);
response.send("error occurred");
});
});
and always get back the error :
"Could not handle the request"
Or I get error on deploy that :
Each then() should return a value or throw
I have a collection called list, inside I have a document named "abc".
Is there something I have to include ? something I have to setup in Firebase to make it work ? anything basic nobody write on the docs ?

Answer 1

Modified following the comments above explaining the OP uses Firestore and not the Realtime Database
You should do as follows. You have to wait that the promise returned by the get() method resolves before sending back the response. For this you need to use the then() method, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then
exports.contentServer = functions.https.onRequest((request, response) => {
admin.firestore().collection('list').doc('abc').get()
.then(docSnapshot => {
console.log(docSnapshot.data());
return response.send(docSnapshot.data()); // or any other value, like return response.send( {result: "success"} );
})
.catch(error => {
console.log("Error getting document:", error);
return response.status(500).send(error);
});
});
As written in the comments above, I would suggest that you watch the 3 videos about "JavaScript Promises" from the Firebase video series: https://firebase.google.com/docs/functions/video-series/

Answer 2

Try this
Updated. Return the response inside then() as what #Renaud Tarnec pointed out.
Using realtime database
exports.contentServer = functions.https.onRequest((request, response) => {
var database = admin.database();
database.ref('list').child('abc').once("value", snapshot => {
const data = snapshot.val();
return response.send(data);
}).catch(error => {
return response.status(500).send(error);
});
});
If you are using firestore.
exports.contentServer = functions.https.onRequest((request, response) => {
const firestore = admin.firestore();
firestore.collection("list").doc('abc').get().then(doc => {
console.log(doc.data());
return response.send(doc.data());
}).catch(error => {
return response.status(500).send(error);
});
});
Important: Don't forget to terminate the request by calling response.redirect(), response.send(), or responses.end() so you can avoid excessive charges from functions that run for too long