@xstate/react

What is @xstate/react?

@xstate/react is a library that provides React hooks for using XState, a state machine and statechart library. It allows you to manage complex state logic in a more structured and predictable way by using finite state machines and statecharts.

What are @xstate/react's main functionalities?

Creating and Using State Machines

This feature allows you to create and use state machines in your React components. The code sample demonstrates a simple toggle button that switches between 'inactive' and 'active' states.

import { useMachine } from '@xstate/react';
import { createMachine } from 'xstate';

const toggleMachine = createMachine({
  id: 'toggle',
  initial: 'inactive',
  states: {
    inactive: { on: { TOGGLE: 'active' } },
    active: { on: { TOGGLE: 'inactive' } }
  }
});

function ToggleButton() {
  const [state, send] = useMachine(toggleMachine);

  return (
    <button onClick={() => send('TOGGLE')}>
      {state.matches('inactive') ? 'Off' : 'On'}
    </button>
  );
}

Using Context for Extended State

This feature allows you to use context for extended state in your state machines. The code sample demonstrates a counter that increments and decrements a count value stored in the machine's context.

import { useMachine } from '@xstate/react';
import { createMachine } from 'xstate';

const counterMachine = createMachine({
  id: 'counter',
  initial: 'active',
  context: { count: 0 },
  states: {
    active: {
      on: {
        INCREMENT: { actions: 'increment' },
        DECREMENT: { actions: 'decrement' }
      }
    }
  }
}, {
  actions: {
    increment: (context) => context.count++,
    decrement: (context) => context.count--
  }
});

function Counter() {
  const [state, send] = useMachine(counterMachine);

  return (
    <div>
      <p>{state.context.count}</p>
      <button onClick={() => send('INCREMENT')}>Increment</button>
      <button onClick={() => send('DECREMENT')}>Decrement</button>
    </div>
  );
}

Invoking Services

This feature allows you to invoke services (e.g., API calls) within your state machines. The code sample demonstrates a state machine that fetches data from an API and handles loading, success, and failure states.

import { useMachine } from '@xstate/react';
import { createMachine, assign } from 'xstate';

const fetchMachine = createMachine({
  id: 'fetch',
  initial: 'idle',
  context: { data: null, error: null },
  states: {
    idle: { on: { FETCH: 'loading' } },
    loading: {
      invoke: {
        src: 'fetchData',
        onDone: { target: 'success', actions: assign({ data: (context, event) => event.data }) },
        onError: { target: 'failure', actions: assign({ error: (context, event) => event.data }) }
      }
    },
    success: { on: { FETCH: 'loading' } },
    failure: { on: { FETCH: 'loading' } }
  }
}, {
  services: {
    fetchData: () => fetch('/api/data').then(response => response.json())
  }
});

function FetchData() {
  const [state, send] = useMachine(fetchMachine);

  return (
    <div>
      {state.matches('idle') && <button onClick={() => send('FETCH')}>Fetch Data</button>}
      {state.matches('loading') && <p>Loading...</p>}
      {state.matches('success') && <pre>{JSON.stringify(state.context.data, null, 2)}</pre>}
      {state.matches('failure') && <p>Error: {state.context.error}</p>}
    </div>
  );
}

Other packages similar to @xstate/react

redux

Redux is a popular state management library for JavaScript applications. It provides a centralized store for state and uses actions and reducers to manage state changes. Unlike @xstate/react, which uses state machines and statecharts, Redux relies on a more traditional approach with a single global state and pure functions to handle state transitions.

mobx

MobX is a state management library that makes state observable and automatically updates the UI when the state changes. It uses reactive programming principles and provides a more flexible and less boilerplate-heavy approach compared to @xstate/react. While @xstate/react focuses on finite state machines, MobX emphasizes reactivity and simplicity.

recoil

Recoil is a state management library for React that provides a more fine-grained approach to state management. It allows you to create atoms (pieces of state) and selectors (derived state) that can be used in your components. Recoil offers a more granular and flexible way to manage state compared to the structured approach of state machines in @xstate/react.

README

@xstate/react

This package contains utilities for using XState with React.

• Read the full documentation in the XState docs.
• Read our contribution guidelines.

Quick start

1. Install xstate and @xstate/react:

npm i xstate @xstate/react

1. Import the useMachine hook:

import { useMachine } from '@xstate/react';
import { createMachine } from 'xstate';

const toggleMachine = createMachine({
  id: 'toggle',
  initial: 'inactive',
  states: {
    inactive: {
      on: { TOGGLE: 'active' }
    },
    active: {
      on: { TOGGLE: 'inactive' }
    }
  }
});

export const Toggler = () => {
  const [state, send] = useMachine(toggleMachine);

  return (
    <button onClick={() => send('TOGGLE')}>
      {state.value === 'inactive'
        ? 'Click to activate'
        : 'Active! Click to deactivate'}
    </button>
  );
};