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in case you are not working with the card template,
you must either install the provider package
or use your own method of accessing the FirebaseFirestore
instance from various parts of your codebase.
<topic_end>
<topic_start>
4. create a firestore controller class
though you can talk to firestore directly,
you should write a dedicated controller class
to make the code more readable and maintainable.
how you implement the controller depends on your game
and on the exact design of your multiplayer experience.
for the case of the card template,
you could synchronize the contents of the two circular playing areas.
it’s not enough for a full multiplayer experience,
but it’s a good start.
to create a controller, copy,
then paste the following code into a new file called
lib/multiplayer/firestore_controller.dart.
<code_start>
import 'dart:async';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/foundation.dart';
import 'package:logging/logging.dart';
import '../game_internals/board_state.dart';
import '../game_internals/playing_area.dart';
import '../game_internals/playing_card.dart';
class FirestoreController {
static final _log = Logger('FirestoreController');
final FirebaseFirestore instance;
final BoardState boardState;
/// for now, there is only one match. but in order to be ready
/// for match-making, put it in a firestore collection called matches.
late final _matchRef = instance.collection('matches').doc('match_1');
late final _areaOneRef = _matchRef
.collection('areas')
.doc('area_one')
.withconverter<list<playingcard>>(
fromFirestore: _cardsFromFirestore, toFirestore: _cardsToFirestore);
late final _areaTwoRef = _matchRef
.collection('areas')
.doc('area_two')
.withconverter<list<playingcard>>(
fromFirestore: _cardsFromFirestore, toFirestore: _cardsToFirestore);
StreamSubscription? _areaOneFirestoreSubscription;
StreamSubscription? _areaTwoFirestoreSubscription;
StreamSubscription? _areaOneLocalSubscription;
StreamSubscription? _areaTwoLocalSubscription;
FirestoreController({required this.instance, required this.boardState}) {
// subscribe to the remote changes (from firestore).
_areaOneFirestoreSubscription = _areaOneRef.snapshots().listen((snapshot) {
_updateLocalFromFirestore(boardState.areaOne, snapshot);
});
_areaTwoFirestoreSubscription = _areaTwoRef.snapshots().listen((snapshot) {
_updateLocalFromFirestore(boardState.areaTwo, snapshot);
});
// subscribe to the local changes in game state.
_areaOneLocalSubscription = boardState.areaOne.playerChanges.listen((_) {
_updateFirestoreFromLocalAreaOne();
});
_areaTwoLocalSubscription = boardState.areaTwo.playerChanges.listen((_) {
_updateFirestoreFromLocalAreaTwo();
});
_log.fine('Initialized');
}
void dispose() {
_areaOneFirestoreSubscription?.cancel();
_areaTwoFirestoreSubscription?.cancel();
_areaOneLocalSubscription?.cancel();
_areaTwoLocalSubscription?.cancel();
_log.fine('Disposed');
}
/// takes the raw JSON snapshot coming from firestore and attempts to
/// convert it into a list of [playingcard]s.
List<PlayingCard> _cardsFromFirestore(
DocumentSnapshot<Map<String, dynamic>> snapshot,
SnapshotOptions? options,
) {
final data = snapshot.data()?['cards'] as list?;
if (data == null) {
_log.info('No data found on firestore, returning empty list');
return [];
}
final list = List.castFrom<Object?, Map<String, object?>>(data);
try {
return list.map((raw) => PlayingCard.fromJson(raw)).toList();
} catch (e) {
throw FirebaseControllerException(
'failed to parse data from firestore: $e');
}
}
/// takes a list of [playingcard]s and converts it into a JSON object
/// that can be saved into firestore.
Map<String, object?> _cardsToFirestore(
List<PlayingCard> cards,
SetOptions? options,
) {
return {'cards': cards.map((c) => c.toJson()).toList()};
}
/// updates firestore with the local state of [area].