/ State

A predictable & observable state container for React apps

A predictable & observable state container for React apps

Restore

A predictable & observable state container for React apps

  • Simple - Reduced boilerplate, minimal interface, refined patterns
  • Observable - Subscriptions to value changes are automatic, eliminating unnecessary renders
  • Predictable - Unidirectional data makes it easy to test, debug and reason about your application
  • Immutable - Frozen state along with thaw/replace updates provide baked in immutability
  • DevTools - Helpful tools, including time travel, provide clear visibility of your state, actions, updates & observers

Restore DevTools

Install

npm install react-restore

Creating a store

A store holds the state of the application and the actions used to update that state

import Restore from 'react-restore'
import * as actions from './actions'
let initialState = {text: 'Hello World'}
let store = Restore.create(initialState, actions)

Now we have a store!

Accessing values in the store

To get the text value from the store

store('text') // 'Hello World'

Updating values in the store

  • actions are used to make updates to the state of the store
  • actions are passed as an object during the store's creation
  • The actions object can be created explicitly or by using import syntax
    • e.g. import * as actions from './actions'
  • actions contain the whole lifecycle of an update making async updates easy to create and track

Let's create an action called setText to update the text value in our store

export const setText = (update, newText) => {
  update(state => {
    state.text = newText
    return state
  })
}

setText can now be called via the store

store.setText('Updated World') 

This would update the value text in the store to 'Updated World'

The update method

  • actions are passed update as their first argument (followed by any arguments you passed to them)
  • The update method is how we replace values held by the store
  • The update method uses a pure updater function to preform these updates

If you look back at our setText action you can see our updater function

state => {
  state.text = newText
  return state
}

The updater function is passed the state (or more likely, part of the state) and returns an updated version of it

Targeting state updates

  • update takes a dot notation path as an optional first argument
  • This path allows you to target part of the state instead of the whole state
  • By doing this, only the components that care about what you're targeting will re-render and the rest will not

For example, our setText action could be

export const setText = (update, newText) => {
 update('text', text => {
   return newText
 })
}

Targeting a more complex state

import Restore from 'react-restore'
import * as actions from './actions'
let initialState = {
  nested: {
    wordOne: 'Hello', 
    wordTwo: 'World'
  }
}
let store = Restore.create(initialState, actions)

Let's create an action called setNestedText to update wordTwo in our store

export const setNestedText = (update, newValue) => {
  update('nested.wordTwo', wordTwo => newValue)
}

Calling it is the same as before

store.setNestedText('Updated World')

This would update the value of wordTwo from 'World' to 'Updated World'

Multi-arg Paths

Instead of concatenating a string for the path passed to store or update, you can define your path with multiple arguments. For example if you had an id (let id = 123) for an item within the state you could break the path into multiple arguments, like so...

let name = store('items', id, 'name') // Gets the value of items[id].name from the store

// When updating, the last argument is always the updater function
update('items', id, 'name', name => 'bar') // Updates the value of items[id].name to 'bar'

Connecting the store to your React components

Connecting React components to the store is easy

Restore.connect(Component)
  • Once a component is connected, it will have access to the store via this.store
  • It will automatically re-render itself when a value it consumes from the store changes
  • A connected component inherits the store of its closest connected parent
  • At the top-level of your app you will explicitly connect a store, since it has no parent to inherit from
  • This top-level store will be passed down to your other connected components
  • We recommend using a single top-level store for your app
Restore.connect(Component, store) // Explicitly connects store to Component
Restore.connect(Component) // Component inherits store from closest parent Component

To access the store from within a connected component, we do the same as before but this time referencing this.store

this.store('text')
// or
this.store.setText('Updated World')

Async Updates

Actions can contain synchronous and asynchronous updates, both are tracked and attributed to the action throughout its lifecycle. Here we'll make our setText action get the newText value from the server and then update the state asynchronously.

export const setText = update => {
  getTextFromServer(newText => {
    update('text', text => newText)
  })
}

It can be useful to compose synchronous and asynchronous updates together. Say you wanted to show a loading message while you fetched the newText value from the server. You could update a loading flag synchronously and then unset it later when you get the response.

export const setText = update => {
  update('loading', loading => true)
  getTextFromServer(newText => {
    update('loading', loading => false)
    update('text', text => newText)
  })
}

Enabling DevTools / Time Travel

  • Restore ships with a dev tools component <Restore.DevTools />
  • Drop it anywhere in your application to enable the dev tools

Standalone Observers

Connected components are observers but you can use this functionality outside of components too!

store.observer(() => {
  console.log(store('text'))
})

This function will run once immediately and again anytime the values it consumes change, in this case our text value

Putting it together

App.jsx


import React from 'react'
import Restore from 'react-restore'

class App extends React.Component {
  render () {
    return (
      <div onClick={() => this.store.setText('Updated World')}>
        {this.store('text')}
      </div>
    )
  }
}

export default Restore.connect(App)

actions.js


export const setText = (update, newText) => {
  update('text', text => {
    return newText
  })
}

index.js


import React from 'react'
import ReactDOM from 'react-dom'
import Restore from 'react-restore'

import App from './App.jsx'
import * as actions from './actions.js'

let initialState = {text: 'Hello World'}
let store = Restore.create(initialState, actions)
let Root = Restore.connect(App, store)

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

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