react-gizmo

React Gizmo

UI Finite State Machine for React

React Gizmo is a cute State Machine that doesn't become a monster if you throw water on it

Quick Start

Installation

yarn add react-gizmo

Usage

PS: react-gizmo uses new React Context API. React 16.3 is needed for this library to work.

import React from 'react';
import ReactDOM from 'react-dom';
import { Machine, State } from 'react-gizmo'

const state = {
  initialState: { text: 'Hello' },
  flow: {
    initial: 'start',
    states: {
      start: { on: {  NEXT: 'end' }},
      end: { on: { NEXT: 'start' }}
    }
  }
}

const MachineApp = () => (
  <Machine log state={state} >
    <React.Fragment>
      <State on="start" render={props =>
        <button onClick={() => props.transition('NEXT',
          { off: 'start', setState: { text: 'World' }}
        )}>
          {props.text}
        </button>
      } />
      <State on="end" render={props =>
        <button onClick={() => props.transition('NEXT',
          { off: 'end', setState: { text: 'Hello' }}
        )}>
          {props.text}
        </button>
      } />
    </React.Fragment>
  </Machine>
)

ReactDOM.render(<MachineApp />, document.getElementById('root'));

API

<Machine />

The <Machine /> wraps your App and is responsible for passing down the props to the <State />. The <Machine /> should have only one children, similar to react-router. The initialState and flow are passed to the machine through the state prop.

Prop	Type	Description
log	bool	If true logs state transitions
state	object	The object containing the state machine and initial State: { initialState: any, flow: statechart }

<State />

The <State /> represents the individual state of your flow. on prop is what glues the state to a specific flow state, and the render prop returns a function with the machine props. The render of <State /> must return a component. It's recommended that the render function returns Class based components since only Class based components can have it's methods called by the Machine on state transitions.

...
states: {
  start: { on: {  NEXT: 'end' }},
  end: { on: { NEXT: 'start' }}
}
...
<State on="start" render={props => ...
<State on="end" render={props => ...

Prop	Type	Description
on	string	Component that will be turned 'on' when flow transitions to a state with same name
render	func	Used to pass State Machine props to a new React Component: props => React.Component

props.transition(state[,options])

As the name suggests, this function is responsible for transitioning your app from one state to another. The first argument is the value of the state to be transitioned, and the second argument can receive a bunch of options. Like off to hide other non-actives <State /> components, setState to update your state/initialState, draftState which temporarily stores your changes until it's published and condition where you can pass xState Guards

Option	Type	Description
off	oneOfType(string, arrayOf(string))	Component(s) that will be turned 'off' when transition is called
setState	object	Mutates initialState keys with passed values
draftState	object	Like setState, but changes take effect only after being published. Newer draftStates will replace unpublished ones.
condition	any	Check xState Contitional Transitions (Guards)

props.transition('NEXT', {
  off: 'end',
  setState: {
    text: 'Will be updated'
  },
  draftState: {
    text: 'Will update again, but only after publish'
  },
  condition: { shouldTransition: this.text.length < 99 }
})

props.publish()

Publishes unpublished state aka. draftState. Draft is merged into State and then draft is cleaned. This is usefull when you are not sure if you want to update your state, I.E if a user clicks a cancel button during an API request.

props.transition('NEXT', { draftState: { text: 'Hello World' } })
console.log(this.props.text) // ''
props.publish()
console.log(this.props.text) // 'Hello World'

props[state]

Your initialState/state, can be accessed directly via props.YOUR_STATE_KEY.

console.log(this.props.text) // Hello

Todo

• Connect state to Redux DevTools
• Flow visualisation
• Examples
• Better integration with other State Managers like Redux and Mobx ie.
• Tests

Thanks

David the creator of xstate who made this library possible and Michele for inspiring me with react-automata. Even if you like react-gizmo I recommend you to give them a try. Also, a big thanks to Ryan Florence for giving a great talk about State Machine.