riverpod 0.6.0-dev

A simple way to access state from anywhere in your application while robust and being testable.

Black Lives Matter. Support the Equal Justice Initiative.

Welcome to Riverpod!

This project can be considered as an experimental provider rewrite.

For learning how to use Riverpod, see its documentation: https://riverpod.dev

Long story short:

• Declare your providers as global variables:

  final myNotifierProvider = ChangeNotifierProvider((_) {
    return MyNotifier();
  });
  
  class MyNotifier extends ChangeNotifier {
    int count;
    // TODO: typical ChangeNotifier logic
  }
  

• Use them inside your widgets in a compile-time safe way. No runtime exceptions!

  class Example extends HookWidget {
    @override
    Widget build(BuildContext context) {
      final count = useProvider(myNotifierProvider);
      return Text(count.toString());
    }
  }
  

See the FAQ if you have questions around what this means for provider.

Index

• Motivation
• FAQ
  • Why another project when provider already exists?
  • Is it safe to use in production?
  • Will this get merged with provider at some point?
  • Will provider be deprecated/stop being supported?

Motivation

If provider is a simplification of InheritedWidgets, then Riverpod is a reimplementation of InheritedWidgets from scratch.

It is very similar to provider in principle, but also has major differences as an attempt to fix the common problems that provider face.

Riverpod has multiple goals. First, it inherits the goals of provider:

• Being able to safely create, observe and dispose states without having to worry about losing the state on widget rebuild.
• Making our objects visible in Flutter's devtool by default.
• Testable and composable
• Improve the readability of InheritedWidgets when we have multiple of them (which would naturally lead to a deeply nested widget tree).
• Make apps more scalable with a unidirectional data-flow.

From there, Riverpod goes a few steps beyond:

• Reading objects is now compile-safe. No more runtime exception.
• It makes the provider pattern more flexible, which allows supporting commonly requested features like:
  • Being able to have multiple providers of the same type.
  • Disposing the state of a provider when it is no longer used.
  • Have computed states
  • Making a provider private.
• Simplifies complex object graphs. It is easier to depend on asynchronous state.
• Makes the pattern independent from Flutter

These are achieved by no longer using InheritedWidgets. Instead, Riverpod implements its own mechanism that works in a similar fashion.

For learning how to use Riverpod, see its documentation: https://riverpod.dev

Contributing

Contributions are welcomed!

Here is a curated list of how you can help:

• Report bugs and scenarios that are difficult to implement
• Report parts of the documentation that are unclear
• Update the documentation / add examples
• Implement new features by making a pull-request

FAQ

Why another project when provider already exists?

While provider is largely used and well accepted by the community, it is not perfect either.

People regularly file issues or ask questions about some problems they face, such as:

• Why do I have a ProviderNotFoundException?
• How can I make that my state automatically disposed of when not used anymore?
• How to make a provider that depends on other (potentially complex) providers?

These are legitimate problems, and I believe that something can be improved to fix those.

The issue is, these problems are deeply rooted in how provider works, and fixing those problems is likely impossible without drastic changes to the mechanism of provider.

In a way, if provider is a candle then Riverpod is a lightbulb. They have very similar usages, but we cannot create a lightbulb by improving our candle.

Is it safe to use in production?

The project is still experimental, so use it at your own risk.

It applied all the lessons learned from provider, so I would expect this project to solve most use-cases.
But if your project randomly catches fire, you were warned!

Will this get merged with provider at some point?

No. At least not until it is proven that the community likes Riverpod and that it doesn't cause more problems than it solves.

While provider and this project have a lot in common, they do have some major differences. Differences big enough that it would be a large breaking change for users of provider to migrate Riverpod.

Considering that, separating both projects initially sounds like a better compromise.

Will provider be deprecated/stop being supported?

Not in the short term, no.

This project is still experimental and unpopular. While it is, in a way, a provider 2.0, its worth has yet to be proven.

Until it is certain that Riverpod is a better way of doing things and that the community likes it, provider will still be maintained.