Adding a map to an array on Firestore Android

Issue

I'm having a little trouble getting my data to save to a Firestore database. Each document in my "meetings" collection has a list of users (maps), but I cannot seem to add anything or create a new document. I read the documentation, and it said to use FieldValue.arrayUnion(), which I tried:

    private fun addUserToMeeting(user: User) {
        val meetingRef = database.collection("meetings").document(meetingID.toString())

        val userData = hashMapOf(
            "email" to user.email,
            "latitude" to user.latitude,
            "longitude" to user.longitude,
            "token" to user.token,
            "username" to user.username
        )

        meetingRef.update("users", FieldValue.arrayUnion(userData))
    }

This is called anytime an "add user to meeting" button is clicked.

Here's a picture of my schema:

Has anyone got some suggestions on what I might be doing wrong?

Solution

If the document doesn't exist yet, you can't use update to create it. As its name implies, update can only be used to update an existing document.

To create a new document at a location you control, use set:

meetingRef.set(hashMapOf("users" to FieldValue.arrayUnion(userData)))

Also see the Firebase documentation on setting a document.

Answered By - Frank van Puffelen