Question 120925 in Firebase Question posted in
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Firebase – How to append a nested array value in Firestore?

I have a firestore documented modeled like this:

In each document, there can be multiple messages, and in each message, there can be multiple comments. Im trying to update the comments with the following:

Future<void> updateStingrayComment(
   Comment? comment, String? stingrayid) async {
    return FirebaseFirestore.instance
        .collection('stingrays')
        .doc(stingrayid)
        .update({
          'messages': {
            'comments': FieldValue.arrayUnion([Comment.toJson(comment)])
          }
        })

I recognize Im not using a messageID to attach the comment to, but I’m not sure how I would do that. Anyone have any ideas? Im using this in flutter, if that makes any difference.

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2

Answers


  1. Chosen as BEST ANSWER
    0

    For anyone with a similar situation, I ended up with a kindof brute force solution. Instead of a nested list of comments, I made a separate list called 'comments'. Every message will have a message ID, which gets passed to respective comments, and all comments will be queried based on their message ID.


  2. 0

    It looks like messages is an array field, and there is no operation to update an item in an array field.

    You will have to:

    1. Read the array from the document into your application code
    2. Update the array in memory
    3. Write the entire array back to the document
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