从 Firestore 集合中获取包含所有文档的列表

Question

I have this simple to query data from Firestore:

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';

class TodoPage extends StatefulWidget {
  const TodoPage({Key? key}) : super(key: key);

  @override
  State<TodoPage> createState() => _TodoPageState();
}

class _TodoPageState extends State<TodoPage> {
  User? user = FirebaseAuth.instance.currentUser;
  late final Stream<QuerySnapshot> _mainStream = FirebaseFirestore.instance
      .collection('users')
      .doc(user!.uid)
      .collection('pendencies')
      .snapshots();

  @override
  Widget build(BuildContext context) {
    Size mediaQuery = MediaQuery.of(context).size;

    return StreamBuilder<QuerySnapshot>(
      stream: _mainStream,
      builder: (context, mainSnapshot) {
        if (mainSnapshot.hasError) {
          return const Center(
            child: Text('Something went wrong'),
          );
        }
        if (mainSnapshot.connectionState == ConnectionState.waiting) {
          return const Center(
            child: CircularProgressIndicator(),
          );
        }
            var pendenciesList = mainSnapshot.data!.docs;
            print(pendenciesList);

            return SafeArea(
              child: SizedBox(
                width: mediaQuery.width,
                height: mediaQuery.height,
                child: const Center(
                  child: Text('Test')
                ),
              ),
            );
          },
        );
      
  }
}

Currently, there are 2 documents in it. Is there a way to store the entire collection (documents and corresponded fields and values) inside a list? If yes, how can I do it?

I've tried var pendenciesList = mainSnapshot.data.;docs; but got [Instance of '_JsonQueryDocumentSnapshot', Instance of '_JsonQueryDocumentSnapshot']

Answer 1

yes you can do that

//the list where you have all the data
List data = [];

...

// function to fill up the data list
getData() async {
  await FirebaseFirestore.instance.collection("collectionName").get.then((value) {
    for(var i in value.docs) {
      data.add(i.data());
    }
  });
}

...

// get a field from a document in the data list
data[index]["field"];

Answer 2

The result of the snapshots() function is of type Stream<QuerySnapshot<Map<String, dynamic>>> meaning that it's like a stream of JSON values that you need to parse manually.

What you need to do is to define a function on your model object that can receive a value of type QueryDocumentSnapshot<Map<String, dynamic>> snapshot and return a value of your model. Here is an example:

@immutable
class CloudNote {
  final String documentId;
  final String ownerUserId;
  final String text;
  const CloudNote({
    required this.documentId,
    required this.ownerUserId,
    required this.text,
  });

  CloudNote.fromSnapshot(QueryDocumentSnapshot<Map<String, dynamic>> snapshot)
      : documentId = snapshot.id,
        ownerUserId = snapshot.data()[ownerUserIdFieldName],
        text = snapshot.data()[textFieldName] as String;
}

Then when you retrieve your snapshots, you can convert them to your model object by mapping them as shown here:

Stream<Iterable<CloudNote>> allNotes({required String ownerUserId}) {
  final allNotes = notes
      .where(ownerUserIdFieldName, isEqualTo: ownerUserId)
      .snapshots()
      .map((event) => event.docs.map((doc) => CloudNote.fromSnapshot(doc)));
  return allNotes;
}