@charliehess/redux-persist

Redux Persist

Persist and rehydrate a redux store.

Redux Persist is performant, easy to implement, and easy to extend.

npm i --save redux-persist

Basic Usage

Basic usage requires adding a few lines to a traditional redux application:

import {compose, applyMiddleware, createStore} from 'redux'
import {persistStore, autoRehydrate} from 'redux-persist'

// add `autoRehydrate` as an enhancer to your store (note: `autoRehydrate` is not a middleware)
const store = createStore(
  reducer,
  undefined,
  compose(
    applyMiddleware(...),
    autoRehydrate()
  )
)

// begin periodically persisting the store
persistStore(store)

For per reducer rehydration logic, you can opt-in by adding a handler to your reducer:

import {REHYDRATE} from 'redux-persist/constants'
//...
case REHYDRATE:
  var incoming = action.payload.myReducer
  if (incoming) return {...state, ...incoming, specialKey: processSpecial(incoming.specialKey)}
  return state

You may also need to configure the persistence layer, or take action after rehydration has completed:

persistStore(store, {blacklist: ['someTransientReducer']}, () => {
  console.log('rehydration complete')
})

And if things get out of wack, just purge the storage

persistStore(store, config, callback).purge()

API

Full API

persistStore(store, [config, callback])

• arguments
  • store redux store The store to be persisted.
  • config object
    • blacklist array keys (read: reducers) to ignore
    • whitelist array keys (read: reducers) to persist, if set all other keys will be ignored.
    • storage object a conforming storage engine.
    • transforms array transforms to be applied during storage and during rehydration.
    • asyncTransforms boolean set to true to allow for asynchronous transforms.
    • debounce integer debounce interval applied to storage calls (in miliseconds).
    • keyPrefix string change localstorage default key (default: reduxPersist:) Discussion on why we need this feature ?
  • callback function will be called after rehydration is finished.
• returns persistor object

persistor object

• the persistor object is returned by persistStore with the following methods:
  • .purge(keys)
    • keys array An array of keys to be purged from storage. If not provided all keys will be purged.
  • .rehydrate(incoming, options)
    • incoming object Data to be rehydrated into the store.
    • options object If serial:true, incoming should be a string, that will be deserialized and passed through the transforms defined in the persistor.
    • Manually rehydrates the store with the passed data, dispatching the rehydrate action.
  • pause()
    • pauses persistence
  • resume()
    • resumes persistence

autoRehydrate(config)

• This is a store enhancer that will automatically shallow merge the persisted state for each key. Additionally it queues any actions that are dispatched before rehydration is complete, and fires them after rehydration is finished.
• arguments
  • config object
    • log boolean Turn on debug mode. Default: false.
    • stateReconciler function override the default shallow merge state reconciliation.

constants

• import * as constants from 'redux-persist/constants'. This includes REHYDRATE and KEY_PREFIX.

Alternate Usage

getStoredState / createPersistor

If you need more control over persistence flow, you can implement getStoredState and createPersistor. For example you can skip autoRehydrate and directly pass restoredState into your store as initialState:

import {getStoredState, autoRehydrate, createPersistor} from 'redux-persist'

const persistConfig = { /* ... */ }

getStoredState(persistConfig, (err, restoredState) => {
  const store = createStore(reducer, restoredState)
  const persistor = createPersistor(store, persistConfig)
})

Secondary Persistor

import {persistStore, createPersistor} from 'redux-persist'
const persistor = persistStore(store) // persistStore restores and persists
const secondaryPersistor = createPersistor(store, {storage: specialBackupStorage}) // createPersistor only persists

Storage Engines

• localStorage (default) web
• sessionStorage
• localForage (recommended) web, see usage below
• AsyncStorage for react-native
• redux-persist-node-storage for use in nodejs environments.
• custom any conforming storage api implementing the following methods: setItem getItem removeItem getAllKeys. [example]

// sessionStorage
import { persistStore } from 'redux-persist'
import { asyncSessionStorage } from 'redux-persist/storages'
persistStore(store, {storage: asyncSessionStorage})

// react-native
import {AsyncStorage} from 'react-native'
persistStore(store, {storage: AsyncStorage})

// web with recommended localForage
import localForage from 'localforage'
persistStore(store, {storage: localForage})

Transforms

Transforms allow for arbitrary state transforms before saving and during rehydration.

• immutable - support immutable reducers
• compress - compress your serialized state with lz-string
• encrypt - encrypt your serialized state with AES
• filter - store or load a subset of your state
• filter-immutable - store or load a subset of your state with support for immutablejs
• expire - expire a specific subset of your state based on a property
• custom transforms:

import { createTransform, persistStore } from 'redux-persist'

let myTransform = createTransform(
  // transform state coming from redux on its way to being serialized and stored
  (inboundState, key) => specialSerialize(inboundState, key),
  // transform state coming from storage, on its way to be rehydrated into redux
  (outboundState, key) => specialDeserialize(outboundState, key),
  // configuration options
  {whitelist: ['specialReducer']}
)

persistStore(store, {transforms: [myTransform]})

• async transforms:

import { createTransform, persistStore } from 'redux-persist'

let myTransform = createTransform(
  async (inboundState, key) => {
    const serialized = await asyncSerialize(inboundState, key)
    return serialized
  },
  async (outboundState, key) => {
    const deserialized = await specialDeserialize(outboundState, key)
    return deserialized
  },
  {whitelist: ['specialReducer']}
)

persistStore(store, {
  transforms: [myTransform],
  asyncTransforms: true
})

Migrations

One challenge developers encounter when persisting state for the first time is what happens when the shape of the application state changes between deployments? Solution: redux-persist-migrate

Action Buffer

A common mistake is to fire actions that modify state before rehydration is complete which then will be overwritten by the rehydrate action. You can either defer firing of those actions until rehydration is complete, or you can use an action buffer.

Why Redux Persist

• Performant out of the box (uses a time iterator and operates on state partials)
• Keeps custom rehydration logic in the reducers (where it intuitively belongs)
• Supports localStorage, react-native AsyncStorage, or any conforming storage api

Because persisting state is inherently stateful, persistStore lives outside of the redux store. Importantly this keeps the store 'pure' and makes testing and extending the persistor much easier.

About Auto Rehydrate

autoRehydrate is a store enhancer that automatically rehydrates state.

While auto rehydration works out of the box, individual reducers can opt in to handling their own rehydration, allowing for more complex operations like data transforms and cache invalidation. Simply define a handler for the rehydrate action in your reducer, and if the state is mutated, auto rehydrate will skip that key.

Auto rehydrate is provided as a convenience. In a large application, or one with atypical reducer composition, auto rehydration may not be convenient. In this case, simply omit autoRehydrate. Rehydration actions will still be fired by persistStore, and can then be handled individually by reducers or using a custom rehydration handler.