flutter-change-notifier

Extend ChangeNotifier in your model class, keep state private, and call notifyListeners() after each mutation. Provide it with ChangeNotifierProvider above the widgets that use it, then read it with Consumer or Provider.of.

Place Consumer widgets as deep in the widget tree as possible so only small subtrees rebuild. Use the Consumer child parameter for widgets that do not depend on the model, and use Provider.of with listen: false for action-only calls.

Use Provider.of<T>(context, listen: false) when you only need to call methods on the model, such as inside an onPressed callback, without subscribing to state changes. This avoids triggering rebuilds for action-only interactions.

Yes, ChangeNotifierProvider automatically disposes of the ChangeNotifier model when it is no longer needed in the widget tree. You do not need to call dispose manually on models created by the provider.

Use MultiProvider with a list of providers, such as multiple ChangeNotifierProvider entries, wrapping your app. Each model remains independently provided and disposed, and widgets can consume any of them by type.

Create the model directly in a test, attach a listener with addListener, perform a mutation, and assert both the state change and that the listener was notified. This verifies notifyListeners() is called on every state change.