value_selectable 2.0.0

A Flutter package that provides computed values for `ValueNotifier`, inspired by the Selectors from Recoil.

ValueSelectable

A Flutter package that provides computed values for ValueNotifier, inspired by the Selectors from Recoil.

Overview

This package includes two main classes:

• ValueSelector: Computes a synchronous value based on a given scope.
• AsyncValueSelector: Computes an asynchronous value based on a given scope.

These classes allow you to create computed values that automatically update when their dependencies change, providing a reactive programming model similar to Recoil selectors.

Features

• Reactive computation of values based on dependencies.
• Synchronous and asynchronous selectors.
• Automatic updates when dependencies change.
• Easy integration with Flutter's ValueNotifier.

Installation

Add the following to your pubspec.yaml:

flutter pub add value_selectable

Usage

ValueSelector

Computes a synchronous value based on a given scope:

import 'package:flutter/widgets.dart';
import 'package:value_selectable/value_selectable.dart';

void main() {
  final valueNotifier = ValueNotifier<int>(1);
  final selector = ValueSelector<int>((get) => get(valueNotifier) + 1);

  print(selector.value); // Outputs: 2

  valueNotifier.value = 2;
  print(selector.value); // Outputs: 3
}

AsyncValueSelector

Computes an asynchronous value based on a given scope.

import 'package:flutter/widgets.dart';
import 'package:value_notifier_selectors/value_notifier_selectors.dart';
import 'dart:async';

void main() async {
  final valueNotifier = ValueNotifier<int>(1);
  final selector = AsyncValueSelector<int>(0, (get) async => get(valueNotifier) + 1);

  await selector.isReady;
  print(selector.value); // Outputs: 2

  valueNotifier.value = 2;
  await Future.delayed(Duration(milliseconds: 300));
  print(selector.value); // Outputs: 3
}

Advance Usage

As classes ValueSelectable trabalham devirando valores de outros ValueListenable, mas isso também pode ser feito por meio de ações utilizando o setter do value de um ValueSelectable. Note que ao alterar esse value nada acontecerá se a função set não for implementada no construtor de uma das classes do ValueSelectable.

Com isso em mente poderemos fazer derivações utilizando ações de uma forma parecida com um Reducer:

  final counterState = ValueNotifier<int>(0);

  final selectorState = ValueSelector<int>(
    (get) => get(counterState) + 1,
    (action) {
      if (action == 'INCREMENT') counterState.value++;
      if (action == 'DECREMENT') counterState.value--;
    },
  );

  // directly change
  counterState.value = 1;

  // indirectly change
  selectorState.value = 'INCREMENT';
  selectorState.value = 'DECREMENT';

Contributing

Contributions are welcome! Please open an issue or submit a pull request.