Simplify State Management in Flutter with Provider

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Simplify State Management in Flutter with Provider

Provider is a powerful package that simplifies state management in Flutter applications. It eliminates the need for manually creating and managing inherited widgets, making your code cleaner and more reusable.

Using Providers

To expose a value:

Provider(
  create: (_) => MyModel(),
  child: ...
)

To read a value:

context.watch()
context.read()

Types of Providers

Provider offers various types of providers for different object types:

  • Provider: Basic provider for any value.
  • ListenableProvider: Listens to Listenable objects and rebuilds dependent widgets when the listener is called.
  • ChangeNotifierProvider: Listens to ChangeNotifier objects and automatically calls ChangeNotifier.dispose when needed.
  • ValueListenableProvider: Listens to ValueListenable objects and exposes only the ValueListenable.value.
  • StreamProvider: Listens to Stream objects and exposes the latest emitted value.
  • FutureProvider: Takes a Future and updates dependents when the future completes.

Benefits of Provider

  • Simplified allocation/disposal of resources
  • Lazy-loading
  • Reduced boilerplate
  • Devtool friendly (state visible in Flutter devtool)
  • Common way to consume InheritedWidgets (Provider.of/Consumer/Selector)
  • Increased scalability for classes with exponential listening mechanisms (e.g., ChangeNotifier)

Usage Examples

Exposing a New Object Instance:

Provider(
  create: (_) => MyModel(),
  child: ...
)

Avoid Using Provider.value for Object Creation:

ChangeNotifierProvider.value(
  value: MyModel(),
  child: ...
)

Reusing an Existing Object Instance:

ChangeNotifierProvider.value(
  value: variable,
  child: ...
)

Reading a Value:

context.watch()

Optionally Depending on a Provider:

context.watch()

MultiProvider:

MultiProvider(
  providers: [
    Provider(create: (_) => Something()),
    Provider(create: (_) => SomethingElse()),
    Provider(create: (_) => AnotherThing()),
  ],
  child: someWidget,
)

ProxyProvider:

ProxyProvider(
  update: (_, counter, __) => Translations(counter.value),
  child: Foo(),
)

FAQ

Can I Inspect the Content of My Objects?

Use Flutter's devtool or override toString or implement Diagnosticable.

Exception When Obtaining Providers in initState?

Use context.watch<T>() instead or explicitly specify that you don't care about updates (e.g., context.read<T>()).

How to Handle Hot-Reload on My Objects?

Make your provided object implement ReassembleHandler.

Do I Have to Use ChangeNotifier for Complex States?

No, you can use any object to represent your state (e.g., Provider.value() with a StatefulWidget).

Can I Make My Own Provider?

Yes, provider exposes all the small components that make a fully-fledged provider.

My Widget Rebuilds Too Often. What Can I Do?

Use context.select to listen only to specific properties on the obtained object or use Consumer with the optional child argument.

Can I Obtain Two Different Providers Using the Same Type?

No, give both providers a different type instead.

Can I Consume an Interface and Provide an Implementation?

Yes, use Provider.of<ProviderInterface>.

Conclusion

Provider is an essential package for managing state in Flutter applications. It simplifies allocation, disposal, and listening to changes, making your code cleaner, more reusable, and more scalable. Embrace Provider to elevate the state management capabilities of your Flutter apps.

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