Lifecycle and Disposal

Proper disposal of state resources prevents memory leaks and unintended behavior across screens or sessions. Follow these rules for common patterns.

Disposal Patterns

• ChangeNotifier: Implement dispose() and call it when the owner is removed from the widget tree. Ensure any addListener calls have corresponding removeListener cleanup if the notifier outlives the listener.
• Bloc/Cubit: Clean up resources in close(). If the Bloc creates standard Dart Streams, ensure they are canceled here.
• Riverpod: For autoDispose providers, rely on Riverpod's internal cleanup, but explicitly register disposal callbacks via ref.onDispose for native resources or non-Riverpod listeners.

Stream and Controller Cleanup

• Close any StreamController created locally. Do this in dispose() or the equivalent lifecycle teardown method.
• Cancel all active StreamSubscription instances when the class that created them is disposed. Do not rely on garbage collection for active subscriptions.

Testing Lifecycle

• Explicitly test the disposal path. Verify that resources are freed, subscriptions are canceled, and no lingering state remains that could pollute the next run.
• Test that calling dispose() twice (if allowed by the framework) is safe or throws appropriately, and verify no updates are emitted post-disposal.

Leak Patterns

• Global Singletons: Do not use global singletons or static variables as a substitute for clear scope boundaries and proper disposal. Global lifespans bypass tree lifecycle hooks.
• Undisposed Controllers: Missing close() calls on controllers or missing cancel() calls on subscriptions are the primary sources of leaks in Flutter apps. Review these carefully.