A tiny state management library for Dart developers.

Why?

Essentially a functional approach to flutter's State except without the flutter.

Usage

A simple usage example:

import 'package:stateful/stateful.dart';

class Person {
  int age;
  String name;

  Person(this.name,this.age);
}

main() {
  var state = Stateful(Person('Joe Smith',39));
  print(state.getState().name); // prints Joe Smith

  var unsub = state.addListener((state) => print('${state.name} is ${state.age}')); // prints Joe Smith is 39
  state.setState(patch: (person) => person..age = person.age+1); // prints Joe Smith is 40
  unsub(); // unsubscribe
  state.setState(patch: (person) => person..age = person.age+1); // doesn't print
}

Selectors

Stolen from reselect. Selectors allow to you select a piece of the state and call a callback only when the selected part of it has changed.

import 'package:stateful/stateful.dart';

class Person {
  int age;
  String name;

  Person(this.name,this.age);
}

main() {
  var state = Stateful(Person('Joe Smith',39));
  

  var unsub = state.addListener(
    Selector1(
      (state) => state.age,
      (age) => print('The person is $age')
    )
  ); // prints The person is 39
  state.setState(patch: (person) => person..age = person.age+1); // prints The person is 40
  state.setState(patch: (person) => person..name = 'Jane Smith'); // doesn't print
}

Dart doesn't support overloading so you need to call a different Selector function (Selector#) depending on how many dependency functions you have.

Features and bugs

Please file feature requests and bugs at the issue tracker.