Package Exports

react-broadcast

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Readme

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.

Installation

Using yarn:

$ yarn add react-broadcast

Then, use as you would anything else:

// using ES6 modules
import { Broadcast, Subscriber } from "react-broadcast"

// using CommonJS modules
var Broadcast = require("react-broadcast").Broadcast
var Subscriber = require("react-broadcast").Subscriber

The UMD build is also available on unpkg:

<script src="https://unpkg.com/react-broadcast/umd/react-broadcast.min.js"></script>

You can find the library on window.ReactBroadcast.

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() {
    return this.props.children
  }
}

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>
          <Subscriber channel="currentUser">
            {currentUser => <p>The current user is {currentUser.name}</p>}
          </Subscriber>
        </UpdateBlocker>
      </Broadcast>
    )
  }
}

By default <Broadcast value> values are compared using the === (strict equality) operator. To change this behavior, use <Broadcast compareValues> which is a function that takes the prevValue and nextValue and compares them. If compareValues returns true, no re-render will occur.

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>

Enjoy!

About

react-broadcast is developed and maintained by React Training. If you're interested in learning more about what React can do for your company, please get in touch!