React Automata
A state machine abstraction for React that provides declarative state management and automatic test generation.
Quick Start
Installation
reactandreact-test-rendererare peer dependencies.
yarn add react-automata
Usage
// App.js
import React from 'react'
import { Action, withStateMachine } from 'react-automata'
const statechart = {
initial: 'a',
states: {
a: {
on: {
NEXT: 'b',
},
onEntry: 'sayHello',
},
b: {
on: {
NEXT: 'a',
},
onEntry: 'sayCiao',
},
},
}
class App extends React.Component {
handleClick = () => {
this.props.transition('NEXT')
}
render() {
return (
<div>
<button onClick={this.handleClick}>NEXT</button>
<Action is="sayHello">Hello, A</Action>
<Action is="sayCiao">Ciao, B</Action>
</div>
)
}
}
export default withStateMachine(statechart)(App)
// App.spec.js
import { testStateMachine } from 'react-automata'
import App from './App'
test('it works', () => {
testStateMachine(App)
})
// App.spec.js.snap
exports[`it works: a 1`] = `
<div>
<button
onClick={[Function]}
>
NEXT
</button>
Hello, A
</div>
`;
exports[`it works: b 1`] = `
<div>
<button
onClick={[Function]}
>
NEXT
</button>
Ciao, B
</div>
`;
API
withStateMachine(statechart[, options])(Component)
The withStateMachine higher-order component accepts an xstate configuration object or an xstate machine, some options and a component.
It returns a new component with special props, action and activity methods and additional lifecycle hooks.
The initial machine state and the initial data can be passed to the resulting component through the initialMachineState and initialData props.
Options, Option, Type, Description, ------, ----, -----------, channel, string, The key of the context on which to set the state., devTools, bool, To connect the state machine to the Redux DevTools Extension., ### Props
transition(event[, updater])
The method to change the state of the state machine.
It takes an optional updater function that receives the previous data and returns a data change.
The updater can also be an object, which gets merged into the current data.
handleClick = () => {
this.props.transition('FETCH')
}
machineState
The current state of the state machine.
It's not recommended to use this value because it couples the component and the state machine.
<button onClick={this.handleClick}>
{this.props.machineState === 'idle' ? 'Fetch' : 'Retry'}
</button>
Action and Activity methods
All the component's methods whose names match the names of actions and activities, are fired when the related transition happen.
Actions receive the state and the event as arguments. Activities receive a boolean that is true when the activity should start, and false otherwise.
For example:
const statechart = {
// ...
fetching: {
on: {
SUCCESS: 'success',
ERROR: 'error',
},
onEntry: 'fetchGists',
},
// ...
}
class App extends React.Component {
// ...
fetchGists() {
fetch('https://api.github.com/users/gaearon/gists')
.then(response => response.json())
.then(gists => this.props.transition('SUCCESS', { gists }))
.catch(() => this.props.transition('ERROR'))
}
// ...
}
Lifecycle hooks
componentWillTransition(event)
The lifecycle method invoked when the transition function has been called.
It provides the event, and can be used to run side-effects.
componentWillTransition(event) {
if (event === 'FETCH') {
fetch('https://api.github.com/users/gaearon/gists')
.then(response => response.json())
.then(gists => this.props.transition('SUCCESS', { gists }))
.catch(() => this.props.transition('ERROR'))
}
}
componentDidTransition(prevMachineState, event)
The lifecycle method invoked when a transition has happened and the state is updated.
It provides the previous state machine, and the event.
The current machineState is available in this.props.
componentDidTransition(prevMachineState, event) {
Logger.log(event)
}
<Action />
The component to define which parts of the tree should be rendered for a given action (or set of actions)., Prop, Type, Description, ----, ----, -----------, is, oneOfType(string, arrayOf(string)), The action(s) for which the children should be shown. It accepts the exact value, a glob expression or an array of values/expressions (e.g. is="fetch", is="show*" or is={['fetch', 'show*'])., channel, string, The key of the context from where to read the state., children, node, The children to be rendered when the conditions match., render, func, The render prop receives a bool (true when the conditions match) and it takes precedence over children., onHide, func, The function invoked when the component becomes invisible., onShow, func, The function invoked when the component becomes visible., ```js
Oh, snap!
```js
<Action
is="showError"
render={visible => (visible ? <div>Oh, snap!</div> : null)}
/>
<State />
The component to define which parts of the tree should be rendered for a given state (or set of states)., Prop, Type, Description, ----, ----, -----------, is, oneOfType(string, arrayOf(string)), The state(s) for which the children should be shown. It accepts the exact value, a glob expression or an array of values/expressions (e.g. is="idle", is="error.*" or is={['idle', 'error.*'])., channel, string, The key of the context from where to read the state., children, node, The children to be rendered when the conditions match., render, func, The render prop receives a bool (true when the conditions match) and it takes precedence over children., onHide, func, The function invoked when the component becomes invisible., onShow, func, The function invoked when the component becomes visible., ```js
Oh, snap!
```js
<State
is="error"
render={visible => (visible ? <div>Oh, snap!</div> : null)}
/>
testStateMachine(Component[, { fixtures, extendedState }])
The method to automagically generate tests given a component wrapped into withStateMachine.
It accepts an additional fixtures option to describe the data to be injected into the component for a given transition, and an extendedState option to control the statechart's conditions - both are optional.
const fixtures = {
initialData: {
gists: [],
},
fetching: {
SUCCESS: {
gists: [
{
id: 'ID1',
description: 'GIST1',
},
{
id: 'ID2',
description: 'GIST2',
},
],
},
},
}
test('it works', () => {
testStateMachine(App, { fixtures })
})
Examples
Frequently Asked Questions
You might find the answer to your question here.
Upgrades
The upgrade process is documented here.
Inspiration
Federico, for telling me "Hey, I think building UIs using state machines is the future".
David, for giving an awesome talk about infinitely better UIs, and building xstate.
Ryan, for experimenting with xstate and React - Ryan's approach to React has always been a source of inspiration to me.
Erik, for writing about statecharts, and showing me how to keep UI and state machine decoupled.