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setState ftw
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Michele Bertoli
October 06, 2017
Programming
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3.5k
setState ftw
"Nobody knows how to do anything without Redux anymore. It's ridiculous." - @mjackson
Let's fix it!
Michele Bertoli
October 06, 2017
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Transcript
setState ftw @MicheleBertoli
My name’s Michele and I’m a React fanboy since 2014
I work in Ads at Facebook, and I contribute to
a pretty sophisticated React UI
setState is the primary method you use to update the
UI in React
Are we really going to talk about setState for 40
minutes?
YES
Ok, why?
“I’m learning React but I don’t understand reducers.” Anonymous, Mar
2017
react
react-redux redux react react-router react-router-redux
react-redux redux react react-router react-router-redux
The community
“Nobody knows how to do anything without Redux anymore. It's
ridiculous.” @mjackson, Jun 2016
“3 Reasons why I stopped using React.setState.” @mweststrate, Jun 2016
“I love setState. In 3 1/2 years, I haven't needed
anything more.” @chantastic, Mar 2017
“You might not need Redux.” @dan_abramov, Sep 2016
Common Pitfalls
setState({ title: 'Here comes the sun' }) console.log(this.state.title)
setState is asynchronous
setState({ counter: this.state.counter + 1 }) setState({ counter: this.state.counter +
1 })
Object.assign( prevState, { counter: this.state.counter + 1 }, { counter:
this.state.counter + 1 }, )
Multiple setState calls get batched
this.state.title = 'Come together'
Mutating the state is an anti-pattern
this.state = { song: { title: 'Let it be', year:
1970, }, }
this.setState({ song: { title: 'Hey Jude', }, })
State changes are shallow merged
setState
yarn add setstate - DON’T TRY THIS AT HOME -
None
“If setState was packaged up as a lib, people would
love it.” @chantastic, Jul 2017
setState enqueues changes to the component state and tells React
that a component and its children need to be re-rendered with the updated state.
setState enqueues changes to the component state and tells React
that a component and its children need to be re-rendered with the updated state.
setState(updater, [callback])
(prevState, props) => stateChange
setState(stateChange, [callback])
Best practices
@dan_abramov, Jul 2016
this.state = { price: `${props.currency}${props.value}`, } Don’t
this.setState({ request: API.get(...), }) Don’t
Testing
this.setState( (prevState, props) => ({ counter: prevState.counter + props.step, })
)
export const increment = (prevState, props) => ({ counter: prevState.counter
+ props.step, })
import { increment } from './updaters' this.setState(increment)
test('increment', () => { const prevState = { counter: 1
} const props = { step: 1 } expect( increment(prevState, props) ).toEqual({ counter: 2 }) })
test('increment', () => { const prevState = { counter: 1
} const props = { step: 1 } expect( increment(prevState, props) ).toMatchSnapshot() })
Separation of concerns
• Container: data and behaviour • Presentational: appearance Container and
Presentational
componentDidMount() { API.get(...).then(s => this.setState(s)) } render() { return <Dumb
{...this.state} /> }
cb() { API.post(...).then(s => this.setState(s)) } render() { return <Dumb
{...this.state} cb={this.cb} /> }
yarn add react-fetching
<ReactFetching url="https://api.punkapi.com/v2/beers" ok={beers => <h1>{beers[0].name}</h1>} />
• Higher-order components • Component => Component • Options =>
Component => Component Composition
yarn add react-refetch
connect(mapPropsToRequests)(Component)
connect(() => ({ f: 'https://api.punkapi.com/v2/beers' }))( ({ f }) =>
f.fulfilled ? <h1>{f.value[0].name}</h1> : null )
Sharing state
Do you even lift (your state up)?
None
None
None
componentDidMount() { API.get(...).then(s => this.setState(s)) } render() { return <div>{this.state.data}</div>
}
componentDidMount() { API.get(...).then(this.props.cb) } render() { return <div>{this.props.data}</div> }
cb(data) { this.setState({ data }) } render() { return <Child
{...this.state} cb={this.cb} /> }
yarn add react-broadcast
<Broadcast channel="state" value={this.state} > {this.props.children} </Broadcast>
<Subscriber channel="state"> {state => ( <div>{state.data}</div> )} </Subscriber>
Time travel
yarn add --dev react-lumberjack
None
Lumberjack.back() Lumberjack.forward()
Functional
dispatch(action) { this.setState( prevState => reducer(prevState, action) ) }
yarn add t-redux
const reducer = buildReducer({ 'INCREMENT': state => ({ counter: state.counter
+ 1, }), }) const initialState = { counter: 0 }
const inc = () => dispatcher.dispatch({ type: 'INCREMENT', }) const
Button = ({ counter }) => ( <button onClick={inc}>{counter}</button> )
withState([reducer], initialState)(Button)
• Best practices • Testing • Separation of concerns •
Sharing state • Time Travel • Functional Recap
State Management
• Higher-order components • Immutability • Pure functions • Generators
• Observables Requirements
• Make informed decisions about your tools • Understand the
tradeoffs involved in each decision Choose wisely
• react-redux uses setState • mobx-react uses forceUpdate Know your
tools
Takeaways
Keep it simple
Lift your state up
Have fun!
Michele Bertoli Front End Engineer at Facebook Author of React
Design Patterns and Best Practices Follow me @MicheleBertoli