flutter_solidart 1.0.0-dev902

A simple State Management solution for Flutter applications inspired by SolidJS

A simple state-management library inspired by SolidJS.

The objectives of this project are:

1. Being simple and easy to learn
2. Do not go against the framework (e.g. Flutter) with weird workarounds.
3. Do not have a single global state, but put multiple states only in the most appropriate places

Learning

For a comprehensive and updated documentation go to The Official Documentation

There are 4 main concepts you should be aware:

1. Signals
2. Effects
3. Resources
4. Solid

Signals

Signals are the cornerstone of reactivity in solidart. They contain values that change over time; when you change a signal's value, it automatically updates anything that uses it.

To create a signal, you have to use the createSignal method:

final counter = createSignal(0);

The argument passed to the create call is the initial value, and the return value is the signal.

// Retrieve the current counter value
print(counter.value); // prints 0
// equal to
print(counter());

// Change the counter value
counter.value++; // Increments by 1
// or
counter.value = 2; // Sets the value to 2
// or
counter.set(3);
// or
counter.update((value) => value * 2); // Update the value based on the current value

If you're using flutter_solidart you can use the SignalBuilder widget to automatically react to the signal value, for example:

SignalBuilder(
  signal: counter,
  builder: (_, value, __) {
    return Text('$value');
  },
)

Effects

Signals are trackable values, but they are only one half of the equation. To complement those are observers that can be updated by those trackable values. An effect is one such observer; it runs a side effect that depends on signals.

An effect can be created by using createEffect. The effect automatically subscribes to any signal and reruns when any of them change. So let's create an Effect that reruns whenever counter changes:

final disposeFn = createEffect((_) {
    print("The count is now ${counter.value}");
});

Resources

Resources are special Signals designed specifically to handle Async loading. Their purpose is wrap async values in a way that makes them easy to interact with.

Resources can be driven by a source signal that provides the query to an async data fetcher function that returns a Future.

The contents of the fetcher function can be anything. You can hit typical REST endpoints or GraphQL or anything that generates a future. Resources are not opinionated on the means of loading the data, only that they are driven by futures.

Let's create a Resource:

// The source
final userId = createSignal(1);

// The fetcher
Future<String> fetchUser() async {
    final response = await http.get(
      Uri.parse('https://swapi.dev/api/people/${userId.value}/'),
    );
    return response.body;
}

// The resource
final user = createResource(fetcher: fetchUser, source: userId);

A Resource can also be driven from a [stream] instead of a Future. In this case you just need to pass the stream field to the createResource method. The [source] field is ignored for the [stream] and used only for a [fetcher].

Using ResourceBuilder you can react to the state of the resource:

ResourceBuilder(
  resource: user,
  builder: (_, userState) {
    return userState.on(
      ready: (data) {
        return Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            ListTile(
              title: Text(data),
              subtitle:
                  Text('refreshing: ${userState.isRefreshing}'),
            ),
            userState.isRefreshing
                ? const CircularProgressIndicator()
                : ElevatedButton(
                    onPressed: user.refetch,
                    child: const Text('Refresh'),
                  ),
          ],
        );
      },
      error: (e, _) {
        return Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Text(e.toString()),
            userState.isRefreshing
                ? const CircularProgressIndicator()
                : ElevatedButton(
                    onPressed: user.refetch,
                    child: const Text('Refresh'),
                  ),
          ],
        );
      },
      loading: () {
        return const RepaintBoundary(
          child: CircularProgressIndicator(),
        );
      },
    );
  },
)

The on method forces you to handle all the states of a Resource (ready, error and loading). The are also other convenience methods to handle only specific states.

Solid

The Flutter framework works like a Tree. There are ancestors and there are descendants.

You may incur the need to pass a Signal deep into the tree, this is discouraged. You should never pass a signal as a parameter.

To avoid this there's the Solid widget.

With this widget you can pass a signal down the tree to anyone who needs it.

You will have already seen Theme.of(context) or MediaQuery.of(context), the procedure is practically the same.

Let's see an example to grasp the concept.

You're going to see how to build a toggle theme feature using Solid, this example is present also here https://github.com/nank1ro/solidart/tree/main/examples/toggle_theme

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    // Provide the theme mode signal to descendats
    return Solid( // [1]
      providers: [
        SolidSignal<Signal<ThemeMode>>(
          create: () => createSignal(ThemeMode.light),
        ),
      ],
      child:
          // using a builder here because the `context` must be a descendant of [Solid]
          Builder(
        builder: (context) {
          // observe the theme mode value this will rebuild every time the themeMode signal changes.
          final themeMode = context.observe<ThemeMode>(); // [2]
          return MaterialApp(
            title: 'Toggle theme',
            themeMode: themeMode,
            theme: ThemeData.light(),
            darkTheme: ThemeData.dark(),
            home: const MyHomePage(),
          );
        },
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({super.key});

  @override
  Widget build(BuildContext context) {
    // retrieve the theme mode signal
    final themeMode = context.get<Signal<ThemeMode>>(); // [3]
    return Scaffold(
      appBar: AppBar(
        title: const Text('Toggle theme'),
      ),
      body: Center(
        child:
            // Listen to the theme mode signal rebuilding only the IconButton
            SignalBuilder( // [4]
          signal: themeMode,
          builder: (_, mode, __) {
            return IconButton(
              onPressed: () { // [5]
                // toggle the theme mode
                if (themeMode.value == ThemeMode.light) {
                  themeMode.value = ThemeMode.dark;
                } else {
                  themeMode.value = ThemeMode.light;
                }
              },
              icon: Icon(
                mode == ThemeMode.light ? Icons.dark_mode : Icons.light_mode,
              ),
            );
          },
        ),
      ),
    );
  }
}

First at [1] we've used the Solid widget to provide the themeMode signal to descendants.

The Solid widgets takes a list of providers: The SolidSignal has a create function that returns a SignalBase. You may create a signal or a derived signal. The value is a Function because the signal is created lazily only when used for the first time, if you never access the signal it never gets created. In the SolidSignal you can also specify an identifier for having multiple signals of the same type.

At [2] we observe the value of a signal. The observe method listen to the signal value and rebuilds the widget when the value changes. It takes an optional id that is the signal identifier that you want to use. This method must be called only inside the build method.

At [3] we get the signal with the given signal type. This doesn't listen to signal value. You may use this method inside the initState and build methods.

At [4] using the SignalBuilder widget we rebuild the IconButton every time the signal value changes.

And finally at [5] we update the signal value.

It is mandatory to pass the type of signal value otherwise you're going to encounter an error, for example:

SolidSignal<Signal<ThemeMode>>(create: () => createSignal(ThemeMode.light))

and context.observe<ThemeMode> where ThemeMode is the type of the signal value. context.get<Signal<ThemeMode>> where Signal<ThemeMode> is the type of signal with its type value.

Examples

Sample features using flutter_solidart:

• Counter
• Toggle theme (dark/light mode)
• Todos
• Github Search

Showcase of all flutter_solidart features

• Showcase of all features

Learn every feature of flutter_solidart including:

1. createSignal
2. Show widget
3. Derived signals with createComputed
4. Effects with basic and advanced usages
5. SignalBuilder, DualSignalBuilder and TripleSignalBuilder
6. createResource and ResourceBuilder
7. Solid and its fine-grained reactivity