Firestore not showing updated document after array update

Question

I have a cloud function in Firebase, and it updates an array inside a document using this method: https://firebase.google.com/docs/firestore/manage-data/add-data#update_elements_in_an_array

However, when I try to then get the updated version of the document, it displays what it was before then array update. Here is my code:

eventUpdated is not showing the correct version before the array update.

if(isPut(request)){

    //All new additions
    const userId = request.body.userId;
    const eventId = request.body.eventId;
    const attStatus = request.body.attStatus;

    try {

        let eventsRef = db.collection('events').doc(eventId);

        if (attStatus === true) {
            // Add a new ID to the "eventAttendanceList" array field.
            let arrUnion = eventsRef.update({
                eventAttendanceList: admin.firestore.FieldValue.arrayUnion(userId)
            });
            // Remove a ID from the "eventNonAttendanceList" array field.
            let arrRm = eventsRef.update({
                eventNonAttendanceList: admin.firestore.FieldValue.arrayRemove(userId)
            });


        }
        else if (attStatus === false) {
            // Add a new ID to the "eventNonAttendanceList" array field.
            let arrUnion = eventsRef.update({
                eventNonAttendanceList: admin.firestore.FieldValue.arrayUnion(userId)
            });
            // Remove a ID from the "eventAttendanceList" array field.
            let arrRm = eventsRef.update({
                eventAttendanceList: admin.firestore.FieldValue.arrayRemove(userId)
            });

        }
        else {
            //If you do anything other than true or false, it will just remove the userId from both attending and non-attending
            let arrUnion = eventsRef.update({
                eventAttendanceList: admin.firestore.FieldValue.arrayRemove(userId)
            });
            let arrRm = eventsRef.update({
                eventNonAttendanceList: admin.firestore.FieldValue.arrayRemove(userId)
            });

        }

            let eventUpdated = await db.collection('events').doc(eventId).get()
            return response.status(200).json({status: "200", message: "Event RSVP successfully updated", event: eventUpdated.data()}).send;


    } catch(err) {
        return response.status(500).json({status: "500", message: "Event RSVP could not be updated"}).send;
    }

} else {
    return response.json({status: "ERR", message: "Please send a PUT request."}).send;
}

user_3371862 · Answer

You are calling a set of asynchronous update() methods but you don't wait that they complete before calling the get() method and sending the response.

So you should also use await for the update() methods, as follows:

let eventsRef = db.collection('events').doc(eventId);

if (attStatus === true) {
    // Add a new ID to the "eventAttendanceList" array field.
    await eventsRef.update({
        eventAttendanceList: admin.firestore.FieldValue.arrayUnion(userId)
    });
    // Remove a ID from the "eventNonAttendanceList" array field.
    await eventsRef.update({
        eventNonAttendanceList: admin.firestore.FieldValue.arrayRemove(userId)
    });
}
else if (attStatus === false) {
    //...
}
else {
    //...
}

let eventUpdated = await db.collection('events').doc(eventId).get()
response.status(200).json({ status: "200", message: "Event RSVP successfully updated", event: eventUpdated.data() }).send;

I make the assumption that you are using an HTTP Cloud Function. Note that you don't need to do return but just call response.redirect(), response.send(), or response.end(). See the doc and the corresponding video.

Also note that if you call several document writes or updates in a row, you might use a batched write.

Firestore not showing updated document after array update

1 Answers