import { createStore, applyMiddleware, combineReducers, compose } from'redux';import*as reducers from'reducers';import*as asyncInitialState from'redux-async-initial-state';// We need outerReducer to replace full state as soon as it loadedconstreducer=asyncInitialState.outerReducer(combineReducers({...reducers,// We need innerReducer to store loading state, i.e. for showing loading spinner// If you don't need to handle loading state you may skip it asyncInitialState:asyncInitialState.innerReducer,}));// Load state function// Should return promise that resolves application stateconstloadStore= () => {returnnewPromise(resolve => {fetch('/store').then(response =>response.json()).then(resolve); });}conststore=createStore( reducer,compose(applyMiddleware(asyncInitialState.middleware(loadStore))));
Partial replace
In case when you're loading only part of your store initially, you can add getCurrentState argument in loadStore function. So, if you have some complex shape of your reducer and you need to replace only some of keys in your store (currentUser in example below):
constloadStore= (getCurrentState) => {returnnewPromise(resolve => {fetch('/current_user.json').then(response =>response.json()).then(user => {resolve({// reuse state that was before loading current user...getCurrentState(),// and replace only `currentUser` key currentUser: user }) }); });}
Reducer
The shape of innerReducer is:
{ loaded:false, loading:false, error:false}
You can add it to you reducer if you want to handle loading state, i.e. to show loading spinner. Here is React example (it uses reducer, described above):