How to get the List of Document Reference from a Snapshot Document resulting from a Firestore query

Question

I can't seem to figure out how to get a List after querying a specific Firestore collection.

I want the function to:

• Query the 'chat' collection on the field 'users'.
• Retrieve only the document (should be only one but could be an error and there's more than one) where users, which is a LIST of Document Reference, matches two specific references: chatUserRef and authUserRef
• The function should return a list of the Document References referring to this chat collection

This is what I am trying:

import 'package:cloud_firestore/cloud_firestore.dart';

Future<List<ChatsRecord>> getChatDoc(
  DocumentReference chatUserRef,
  DocumentReference authUserRef,
) async {
  // Add your function code here!

  final firestore =
      FirebaseFirestore.instance; // Get a reference to the Firestore database
  final collectionRef =
      firestore.collection('chats'); // Get a reference to the collection
  final filteredDocuments = collectionRef.where('users', isEqualTo: [
    authUserRef,
    chatUserRef
  ]); // Use the `where` method to filter the list of documents

  final queryDocuments = await filteredDocuments
      .get(); // You can then use the get method on this Query object to retrieve the list of documents AS a Snapshot Document (this is NOT a list of the Documents themselves).

  List<ChatsRecord> listChatDocs = [];

  // Cast the Snapshot Documents to a map
  // Extract the Document Reference ID
  // cast the query document to a map for e
  // (should I forEach?)
  List<ChatsRecord> listChatDocs  = queryDocuments.docs.map((e) {
          return FirebaseFirestore.instance.doc('chats/$e.id');
        }).toList();

  return listChatDocs;
}

Answer 1

Does your ChatsRecord object contain fromSnapshot factory method like this?:

  factory ChatsRecord.fromSnapshot(DocumentSnapshot snapshot) {
    Map<String, dynamic> data = snapshot.data();
    return ChatsRecord(
      chatId: snapshot.id,
      users: data['users'],
      lastMessageTime: data['lastMessageTime'],
    );
  }

If no, create factory function similar to mentioned above in your ChatsRecord class and try to do forEach your queryDocuments in your last code snippet:

List<ChatsRecord> listChatDocs = [];

  queryDocuments.docs.forEach((docSnapshot) {
    // Convert each document snapshot into a ChatsRecord object
    ChatsRecord chat = ChatsRecord.fromSnapshot(docSnapshot);
    // Add the ChatsRecord object to the list
    listChatDocs.add(chat);
  });