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| import 'package:cloud_firestore/cloud_firestore.dart'; | |
| import 'package:firebase_auth/firebase_auth.dart'; | |
| import 'package:riverpod/riverpod.dart'; | |
| // 1つ目のStreamProvider | |
| final authUserProvider = | |
| StreamProvider<User?>((ref) => FirebaseAuth.instance.userChanges()); | |
| // 2つ目のStreamProvider | |
| // authUserProviderをwatchした値を使ってFirestoreから得られるStreamを返す | |
| final userSnapshotProvider = StreamProvider((ref) async* { | |
| final uid = | |
| await ref.watch(authUserProvider.selectAsync((user) => user?.uid)); | |
| if (uid == null) { | |
| // 値を返す時は`yield`を使う | |
| yield null; | |
| return; | |
| } | |
| // Streamを返すときは`yield*`を使う | |
| // (実際には`.withConverter`挟むのが良い) | |
| yield* FirebaseFirestore.instance.collection('users').doc(uid).snapshots(); | |
| }); | |
| // こういう時はFutureProviderで済む | |
| // (元のコード例では不自然にStreamProviderになっていた) | |
| final isSignedInProvider = FutureProvider<bool>((ref) async { | |
| final user = await ref.watch(authUserProvider.future); | |
| return user != null; | |
| }); | |
| // 別解 | |
| final isSignedInProvider2 = FutureProvider<bool>( | |
| (ref) => ref.watch(authUserProvider.selectAsync((user) => user != null)), | |
| ); | |
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