Tag: state-management

ref.watch subscribes and rebuilds, ref.read reads once and never rebuilds. Use watch in every build method and read only inside event callbacks. Here is the decision matrix, the source of both methods in flutter_riverpod 3.4.3, and the four silent failure modes: watch in a callback, read in a provider body, read on an autoDispose provider, and read used as an optimization.

A Key is the identity half of Widget.canUpdate, the one line of framework code that decides whether an Element and its State are reused or thrown away. Here is what that means in practice, the exact list edits that corrupt state without keys, which key type to reach for, and where the key has to sit to work.

Pick by the return type of build(): T means Notifier, FutureOr<T> means AsyncNotifier, Stream<T> means StreamNotifier. Here is the decision matrix, the type hierarchy that explains why, and the == filtering and state-clobbering gotchas that bite each one. Verified against flutter_riverpod 3.4.2 on Flutter 3.44.2.

A step-by-step move from widget-local setState to a Riverpod 3.x Notifier: classify what actually leaves the widget, write the Notifier, convert to ConsumerWidget, and survive the == filtering, build() re-entry, and autoDispose defaults that bite setState refugees. Tested on Flutter 3.44, Dart 3.x, flutter_riverpod 3.3.2.

In Riverpod 3.0 every provider filters listener notifications with ==, not identity. A StreamProvider that re-emits the same mutable object stops rebuilding the UI after the first frame. Here is why it happens and three ways to fix it. Tested on flutter_riverpod 3.3.2, Flutter 3.44, Dart 3.x.

Riverpod 3.0 retries a failed provider up to 10 times by default. Pass a retry function that returns null on ProviderScope, ProviderContainer, or an individual provider to turn it off or bound it.

A step-by-step upgrade from flutter_riverpod 2.x to 3.x: bump the packages, move StateProvider and friends to the legacy import, drop the AutoDispose and Family ref types, handle ProviderException wrapping and automatic retry, and fix the == notification filtering that silently drops StreamProvider events. Tested on Flutter 3.44, Dart 3.x, flutter_riverpod 3.3.2.

Riverpod 3.0 wraps errors thrown while reading a provider in a ProviderException. Catch that type and read e.exception to get your original error back, or use AsyncValue.error which is unwrapped.

In a Notifier, resolve dependencies before the await, then guard the state write with if (!ref.mounted) return. This is the Riverpod 3.0 replacement for the old onDispose mixin, and it stops UnmountedRefException when a provider is disposed mid-await. Tested on flutter_riverpod 3.x, Flutter 3.44, Dart 3.x.

A step-by-step migration from the provider package to Riverpod 3.x in a real Flutter app: ChangeNotifierProvider to Notifier, MultiProvider to ProviderScope, context.watch to ref.watch, ProxyProvider to ref.watch composition, plus the equality and lifecycle gotchas that bite. Tested on Flutter 3.27.1, Dart 3.11, provider 6.1.5, flutter_riverpod 3.3.1.