How can I check the length of a firebase document using stream builder

Question

In my flutter firebase app, I am able to get the length of a user's activity document in firebase using a query snapshot. However, I want the number of documents to update in real-time without the user needing to refresh the page. Can I do that by converting the codes below using stream builder to get the real-time length and how can I do that? this is the code am using now which works perfectly well but doesn't update in real-time.

 //this is the code I want to convert to stream 
    //builder.
  static Future<int> numActivities(String userId) 
     async {
     QuerySnapshot userActivitiesSnapshot = await 
      activitiesRef
    .document(userId)
    .collection('userActivities')
    .where('seen', isEqualTo: '')
    .getDocuments();
    return userActivitiesSnapshot.documents.length;
    }

Solution 1

You need to use the docs property, which "returns a List containing DocumentSnapshot classes", as follows:

return userActivitiesSnapshot.docs.length;

Solution 2

To get a stream of documents, you need to use the .snapshots() method which returns a Stream of QuerySnapshot instead of the .getDocuments() (deprecated in favor of .get()) method which returns a Future of QuerySnapshot.

Then you can map Stream<Snapshot> into a stream of the length of the snapshot's documents.

Your numActivities method should look like this:

 static Stream<int> numActivities(String userId) {
    return activitiesRef
        .document(userId)
        .collection('userActivities')
        .where('seen', isEqualTo: '')
        .snapshots()
        .map((documentSnapshot) => documentSnapshot.docs.length);
  }

Using this in your use case, you need to listen to the stream and update the _activityCount variable.

 _setUpactivityCount() async {
  final String currentUserId =
      Provider.of<UserData>(context, listen: false).currentUserId;
  DatabaseService.numActivities(currentUserId).listen((activityCount) {
    if (mounted) {
      setState(() {
        _activityCount = activityCount;
      });
    }
  });
}

Make sure you take care of _activityCount being null in it's initial state.

Comments

[Emmanuel]

Is it possible for you to mark as Accepted the answer that helped you to solve your problem? This would help the community to notice what's the best approach according to your question by giving visibility of the best answer.

[Enam]

thank you for your contribution, this is the second time you have contributed to helping me solve a problem and I appreciate it

[Enam]

thank you very much. but I think am facing a new problem using your method above. am getting the error Stream<int> cannot be assigned to a variable of type int. I am using a method on the feed page, in initSate to get the stream value. I have just added the new Code.

[Victor Eronmosele]

You need to listen to the stream events and you can get the actual value from there.

[Enam]

Thank you very much.Been trying to figure this out for some time now. You cannot imagine how grateful I am.

[Victor Eronmosele]

Glad I could help :)