supabase-flutter-idioms

# Writing supabase_flutter v3 code Most published Supabase Dart examples are v2 code. v3 changed many of the APIs those examples use, so do not copy a pattern from memory without checking it against this file. To upgrade an existing v2 project, use the `supabase-flutter-migrate-v3` skill instead. ## Rules - Query tables with `table()` and the generated schema, never with `from()` and `Map<String, dynamic>`, unless the table is missing from the generated file. - Generate the schema with the Supabase CLI (2.122.0 or newer) and never edit it by hand. Regenerate it after every database migration: `supabase gen types --lang dart --local > lib/supabase_schema.g.dart`. The `supabase-typegen-generate` skill, installed with the `supabase_typegen` dev dependency, covers the setup and the options. - Pass `publishableKey`. `anonKey` does not exist in v3. - Listen to realtime with streams. v3 has no `callback:` parameters. - Catch the `SupabaseException` hierarchy, never `ClientException`, `TimeoutException` or `String`. - A typed `update()` or `delete()` does nothing until `.where(…)` or `.all()` is called on it. The analyzer reports a missing one as an `unused_result` warning. - Use one client, `Supabase.instance.client`, for the whole app. ## Client setup ```dart file import 'package:flutter/widgets.dart'; import 'package:supabase_flutter/supabase_flutter.dart'; Future<void> main() async { WidgetsFlutterBinding.ensureInitialized(); await Supabase.initialize( url: 'https://your-project.supabase.co', publishableKey: 'your-publishable-key', ); runApp(const SizedBox()); } final supabase = Supabase.instance.client; ``` `Supabase.initialize` persists the session with `SharedPreferencesAsync` and restores it before it returns. Pass `FlutterAuthClientOptions(asyncStorage: …)` to store it elsewhere, for example in secure storage. ## Reading rows The generated file has, per table, a row type (`BooksRow`), insert and update types (`BooksInsert`, `BooksUpdate`) and a class (`Books`) with the table definition and one constant per column and relation. A table in another schema carries the schema as a prefix, `InventoryBooks`. ```dart final List<BooksRow> books = await supabase .table(Books.table) .select() .where(Books.inPrint.isTrue() & Books.price.lt(10)) .order(Books.createdAt.desc()) .limit(20); final String title = books.first.title; final BooksRow book = await supabase .table(Books.table) .select() .where(Books.id.eq(1)) .single(); ``` Filters are methods on the column constants, combined with `&`, `|` and `not()`. Values must match the column type, and `isNull()` only exists on nullable columns. `order()` sorts ascending unless the ordering says `.desc()`. Read some columns only, or embed related rows, with `selectOnly`, and read the values back through the same constants: ```dart final books = await supabase.table(Books.table).selectOnly([ Books.title, Books.authors(Authors.name), ]); final String title = books.first.read(Books.title); final String? authorName = books.first.read(Books.authors)?.read(Authors.name); ``` ## Writing rows ```dart await supabase .table(Books.table) .insert(BooksInsert(authorId: 2, title: 'Dune')); final BooksRow inserted = await supabase .table(Books.table) .insert(BooksInsert(authorId: 2, title: 'Emma')) .select() .single(); await supabase .table(Books.table) .update(BooksUpdate(inPrint: false).setPriceToNull()) .where(Books.id.eq(1)); await supabase.table(Books.table).delete().where(Books.id.eq(1)); ``` - Several rows go through `insertAll()` and `upsertAll()`. - A `null` argument to `BooksInsert` or `BooksUpdate` leaves the column out. Write SQL `NULL` with the generated `set…ToNull()` methods. - Writes resolve to `void`. Add `.select()` to get the written rows back. - `upsert()` takes `onConflict` as a list of columns, `onConflict: [Authors.name]`. ## Calling database functions Every function PostgREST exposes gets a typed method on `rpc`: ```dart final BooksRow? book = await supabase.rpc.bookById(bookId: 1); ``` `supabase.rpc('fn', params: {...})` is the untyped fallback for functions the generator gives no method, which it explains in a comment in the generated file. ## Auth Sign-in methods that always produce a session return the `Session`: ```dart final session = await supabase.auth.signInWithPassword( email: 'user@example.com', password: 'a-strong-password', ); final user = session.user; ``` `signUp()` and `verifyOTP()` still return an `AuthResponse`, since they can complete without a session. `AuthState` is sealed, with one subtype per event. Every new listener first receives `AuthInitialSession` with the current session or `null`. A failed token refresh, for example while offline, is an error of the stream, so every listener passes `onError`: ```dart final subscription = supabase.auth.onAuthStateChange.listen( (state) { switch (state) { case AuthInitialSession(:final session): // The session when this listener attached, or null. print(session?.user.id); case AuthSignedIn(:final session): print('Signed in as ${session.user.email}'); case AuthSignedOut(): print('Signed out'); case _: } }, onError: (Object error) => print('Auth error: $error'), ); ``` `user.userMetadata` is never null, and `user.appMetadata` is an `AppMetadata` with typed `provider` and `providers`. ## Realtime Keep a list of rows up to date with `stream()`: ```dart final Stream<List<BooksRow>> books = supabase .table(Books.table) .stream(primaryKey: [Books.id]) .filter(Books.authorId.eq(2)) .order(Books.title); ``` The `supabase-flutter-realtime` skill covers broadcast, presence and channel status in more depth. React to individual changes with `onTableChanges`. Create the stream before `subscribe()`, and remove the channel when done: ```dart final channel = supabase.channel('books'); final subscription = channel .onTableChanges(Books.table, filters: [Books.authorId.eq(2)]) .listen((change) { switch (change) { case TypedPostgresInsert(:final newRow): print('Added ${newRow.title}'); case TypedPostgresUpdate(:final newRow): print('Changed ${newRow.title}'); case TypedPostgresDelete(:final oldRow): print('Removed ${oldRow.read(Books.id)}'); } }); channel.subscribe(); await subscription.cancel(); await supabase.removeChannel(channel); ``` Broadcast and connection status are streams too: ```dart final channel = supabase.channel('room'); channel .onBroadcast(event: 'cursor') .listen((message) => print(message['payload'])); channel.onStatusChange.listen((change) async { if (change.status == RealtimeSubscribeStatus.subscribed) { await channel.sendBroadcastMessage(event: 'cursor', payload: {'x': 1}); } }); channel.subscribe(); ``` The table must be added to the `supabase_realtime` publication in the database, or no changes arrive. Create a stream once in `State`, never inside `build()`, or every rebuild resubscribes: ```dart file import 'package:flutter/widgets.dart'; import 'package:my_app/supabase_schema.g.dart'; import 'package:supabase_flutter/supabase_flutter.dart'; class BookList extends StatefulWidget { const BookList({super.key}); @override State<BookList> createState() => _BookListState(); } class _BookListState extends State<BookList> { final _books = Supabase.instance.client .table(Books.table) .stream(primaryKey: [Books.id]); @override Widget build(BuildContext context) { return StreamBuilder<List<BooksRow>>( stream: _books, builder: (context, snapshot) { final books = snapshot.data ?? const []; return Column(children: [for (final book in books) Text(book.title)]); }, ); } } ``` ## Errors Every exception the SDK throws for a failed request extends `SupabaseException`. `SupabaseApiException` means the server answered with an error, and `SupabaseTransportException` means no response arrived, including a timeout: ```dart try { await supabase.table(Books.table).select(); } on SupabaseApiException catch (error) { print('${error.statusCode} ${error.errorCode}: ${error.message}'); } on SupabaseTransportException catch (error) { print('No response: ${error.cause}'); } ``` Each service also has its own base, such as `PostgrestException`, `AuthException` or `StorageException`, to catch the errors of one service only. `AuthApiException` and `PostgrestApiException` carry the server's `errorCode`. ## Logging The SDK never prints. It logs through `package:logging` under the `supabase` logger, so listen to it to see the records: ```dart file import 'package:logging/logging.dart'; void enableSupabaseLogs() { Logger.root.onRecord.listen((record) { if (record.loggerName.startsWith('supabase.')) { print('${record.loggerName}: ${record.level.name}: ${record.message}'); } }); } ``` ## Tests Use the `supabase_test` package as a dev dependency instead of mocking the HTTP client by hand. Its `MockSupabaseHttpClient`, `testSupabaseClient` and `signInTestUser` answer requests and put a client in a signed-in state. The `supabase-test-testing` skill, installed with the `supabase_test` dev dependency, covers stubbing, assertions, auth and realtime in tests.