I'm currently trying to make an app that need to read data just for one time from a nested Firestore Database.

Here's my currently working code

FirebaseFirestore firestore = FirebaseFirestore.instance;
    CollectionReference users = firestore.collection('users');
    FirebaseAuth _auth = FirebaseAuth.instance;

    FutureBuilder getTheData = FutureBuilder<DocumentSnapshot>(
      future: users.doc(_auth.currentUser!.uid).get(),
      builder:
          (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {
        if (snapshot.hasError || (snapshot.hasData && !snapshot.data!.exists)) {
          return Text("Something went wrong");
        }
        if (snapshot.connectionState == ConnectionState.done) {
          Map<String, dynamic> data =
              snapshot.data!.data() as Map<String, dynamic>;

          String _condition = data['condition'];
          String _descCondition = data['descCondition'];
          int _percentageValue = data['percentageValue'];

          return defaultDraw(
            condition: _condition,
            descCondition: _descCondition,
            percentageValue: _percentageValue,
          );
        }

        return defaultDraw(
          condition: "Loading",
          descCondition: "",
          percentageValue: 0,
        );
      },
    );

and it's able to read this data (condition, descCondition, and percentageValue) :

but when I'm trying to read this data : Which is another collection inside of the previous document (a collection named 'adviceData' with random document ID that I'm trying to read), I'm getting an error like this :

Here's my code :

FirebaseFirestore firestore = FirebaseFirestore.instance;
    CollectionReference users = firestore.collection('users');
    FirebaseAuth _auth = FirebaseAuth.instance;

    FutureBuilder _getParameterData = FutureBuilder<DocumentSnapshot>(
      future: users
          .doc(_auth.currentUser!.uid)
          .collection('adviceData')
          .doc()
          .get(),
      builder:
          (BuildContext context, AsyncSnapshot<DocumentSnapshot> snapshot) {
        if (snapshot.hasError || (snapshot.hasData && !snapshot.data!.exists)) {
          return Text("Something went wrong");
        }
        if (snapshot.connectionState == ConnectionState.done) {
          Map<String, dynamic> data =
              snapshot.data!.data() as Map<String, dynamic>;

          String _advicePhLow = data['advicePhLow'];
          String _advicePhHigh = data['advicePhHigh'];
          String _adviceTempLow = data['adviceTempLow'];
          String _adviceTempHigh = data['adviceTempHigh'];
          String _adviceHeightLow = data['adviceHeightLow'];
          String _adviceHeightHigh = data['adviceHeightHigh'];

          return drawParameter(
            advicePhLow: _advicePhLow,
            adviceTempLow: _adviceTempLow,
            adviceHeightLow: _adviceHeightLow,
          );
        }

        return drawParameter();
      },
    );

and my question is :

1. Where did I make mistakes?
2. Is there any better method to get a data from firestore?

Thanks in advance

CodePudding user response：

If you want to get all documents from the subcollection adviceData you would need to get a QuerySnapshot like here:

FutureBuilder<QuerySnapshot>(
      future: users
          .doc(_auth.currentUser!.uid)
          .collection('adviceData')
          .get(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (snapshot.hasError) {
          return Text('Something went wrong');
        }

        if (snapshot.connectionState == ConnectionState.waiting) {
          return Text("Loading");
        }

        return ListView(
          children: snapshot.data!.docs.map((DocumentSnapshot document) {
          Map<String, dynamic> data = document.data()! as Map<String, dynamic>;
            return ListTile(
              title: Text(data['full_name']),
              subtitle: Text(data['company']),
            );
          }).toList(),
        );
      },
    );
  }

If you want to get a single document from that subcollection you would need to define the id of that specific document:

 FutureBuilder _getParameterData = FutureBuilder<DocumentSnapshot>(
      future: users
          .doc(_auth.currentUser!.uid)
          .collection('adviceData')
          .doc('documentID') // here
          .get(),
      builder:

You can find more about both methods here.