I want to get realtime data from Firebase Firestore, I am trying to use stream but cant seem to be getting it

Question

I am an absolute beginner at this, so please help. My goal here is to achieve to create a new document inside collection called sensors on Firestore, everytime a new user registers. I am able to get that done, but then I want to fetch field of the document with that specific user's userid only. I have tried following code as well but it gets me a list of all created documents, I only want a single particular document with particular userid.

The following solution I tried was from a youtuber TheNetNinja, but it gets entire list of all documents in my collection:

  //sensor list from snapshot
  List<Sensor> _sensorListFromSnapshot(QuerySnapshot snapshot) {
    return snapshot.documents.map((doc) {
      return Sensor(
        fireRead: doc.data['fireRead'] ?? false,
        airQuality: doc.data['airQuality'] ?? 0,
        carbonMonoxide: doc.data['carbonMonoxide'] ?? 0,
        lpg: doc.data['lpg'] ?? 0,
        smoke: doc.data['smoke'] ?? 0,
      );
    }).toList();
  }

  //get sensors stream
  Stream<List<Sensor>> get sensors {
    return sensorData.snapshots().map(_sensorListFromSnapshot);
  }

So then I ended up trying follwing code just by guessing because I dont really understand these Streams- Providers and other classes of dart-flutter:

 Sensor specificSensorFromSnapshot(DocumentSnapshot event) {
    return Sensor(
      fireRead: event.data['fireRead'] ?? false,
      airQuality: event.data['airQuality'] ?? 0,
      carbonMonoxide: event.data['carbonMonoxide'] ?? 0,
      lpg: event.data['lpg'] ?? 0,
      smoke: event.data['smoke'] ?? 0,
    );
  }

  Stream<Sensor> get sensor {
    final DocumentReference specificSensorData =
        Firestore.instance.collection('sensors').document(uid);
    return specificSensorData.snapshots().map(specificSensorFromSnapshot);
  }

I have a model class called Sensor:

class Sensor {
  final int airQuality;
  final bool fireRead;
  final int carbonMonoxide;
  final int smoke;
  final int lpg;

  Sensor(
      {this.fireRead,
      this.smoke,
      this.carbonMonoxide,
      this.airQuality,
      this.lpg});
}

gso_gabriel gso_gabriel · Accepted Answer · 2020-02-17T08:02:36

There are many ways of returning documents using the document id.

I would recommend you to take a look at the below questions already answered by the community. They are not exactly your case - they are in other programming languages - but they should provide you some approaches on how to return only documents per a specific id, on your case, the id from the user.

Let me know if the information helped you!

I want to get realtime data from Firebase Firestore, I am trying to use stream but cant seem to be getting it

1 Answers