react-broadcast

react-broadcast

react-broadcast provides a reliable way for React components to propagate state changes to their descendants deep in the component hierarchy, bypassing intermediaries who return false from shouldComponentUpdate.

It was originally built to solve issues that arose from using react-router together with react-redux. The router needed a safe way to communicate state changes to <Link>s deep in the component hierarchy, but react-redux relies on shouldComponentUpdate for performance. react-broadcast allows the router to work seamlessly with Redux and any other component that uses shouldComponentUpdate.

Please note: As with anything that uses context, this library is experimental. It may cease working in some future version of React. For now, it's a practical workaround for the router. If we discover some better way to do things in the future, rest assured we'll do our best to share what we learn.

Usage

The following is a totally contrived example, but illustrates the basic functionality we're after:

import React from 'react'
import { Broadcast, Subscriber } from 'react-broadcast'

const users = [
  { name: 'Michael Jackson' },
  { name: 'Ryan Florence' }
]

class UpdateBlocker extends React.Component {
  shouldComponentUpdate() {
    // This is how you indicate to React's reconciler that you don't
    // need to be updated. It's a great way to boost performance when
    // you're sure (based on your props and state) that your render
    // output will not change, but it makes it difficult for libraries
    // to communicate changes down the hierarchy that you don't really
    // know anything about.
    return false
  }

  render() {
    // We can get around the blocker using a <Subscriber>
    return (
      <Subscriber channel="currentUser">
        {currentUser => <p>The current user is {currentUser.name}</p>}
      </Subscriber>
    )
  }
}

class App extends React.Component {
  state = {
    currentUser: users[0]
  }

  componentDidMount() {
    // Randomly change the current user every 2 seconds.
    setInterval(() => {
      const index = Math.floor(Math.random() * users.length)
      this.setState({ currentUser: users[index] })
    }, 2000)
  }

  render() {
    return (
      <Broadcast channel="currentUser" value={this.state.currentUser}>
        <UpdateBlocker/>
      </Broadcast>
    )
  }
}

You may prefer to wrap these components into channel-specific pairs to avoid typos and other problems with the indirection involved with the channel strings:

// Broadcasts.js
import { Broadcast, Subscriber } from 'react-broadcast'

const CurrentUserChannel = 'currentUser'

export const CurrentUserBroadcast = (props) =>
  <Broadcast {...props} channel={CurrentUserChannel}/>

export const CurrentUserSubscriber = (props) =>
  <Subscriber {...props} channel={CurrentUserChannel}/>

// App.js
import { CurrentUserBroadcast, CurrentUserSubscriber } from './Broadcasts'

<CurrentUserBroadcast value={user}/>
<CurrentUserSubscriber>{user => ...}</CurrentUserSubscriber>

That's it! Enjoy :)