如何使用中间件在 Redux 应用程序中编写 localStorage？

Question

我正在创建一个应用程序，它使用 openweather API 获取用户输入的城市列表及其各自的天气。因此，我希望在刷新页面后保留这些城市。我知道如何使用浏览器 localStorage API 持久化数据。但我不知道如何通过中间件将其持久化并将其传递给提供者。

以下是我的主要 Index.js 文件-：

import React from 'react';
import ReactDOM from 'react-dom';
import { Provider } from 'react-redux';
import { createStore, applyMiddleware } from 'redux';
import ReduxPromise from 'redux-promise';

import App from './components/app';
import reducers from './reducers';
import {loadState,saveState} from './localStorage';

const persistedState=loadState();
const store=createStore(persistedState);

store.subscribe(()=>{
store.getState()
});

const createStoreWithMiddleware =
     applyMiddleware(ReduxPromise)(createStore);

ReactDOM.render(
<Provider store={createStoreWithMiddleware(reducers)}>
<App />
</Provider>
, document.querySelector('.container-fluid'));

这是localStorage.js文件-：

export const loadState=()=>{
try{
    const serializedState=localStorage.getItem('state');
    if(serializedState===null){
        return undefined;
    }
    return JSON.parse(serializedState);
}catch(err){
    return undefined;
}
};

export const saveState=(state)=>{
try {
    const serializedState=JSON.stringify(state);
    localStorage.setItem('state',serializedState);
}catch(err){
    console.log(err);
}};

我已经在 reducers 文件夹的不同文件中编写了 reducer。

reducers/index.js -:

import { combineReducers } from 'redux';
import WeatherReducer from './reducer_weather';

const rootReducer = combineReducers({
weather:WeatherReducer
});

export default rootReducer;

还有另一个减速器 reducers/reducer_weather.js -:

import {FETCH_WEATHER} from '../actions/index';
import {DELETECITY} from '../actions/deleterow';
export default function(state=[],action){

switch(action.type){
    case FETCH_WEATHER:
        console.log([action.payload.data, ...state]);
        return [action.payload.data, ...state];
    case DELETECITY:
        console.log([...state].filter((weather)=>{
            return weather.city.id!==action.payload
        }));
        return [...state].filter((weather)=>{
            return weather.city.id!==action.payload
        });
    default:
        return state;

    }; 
}

在使用 localStorage 持久化应用程序状态之前，我的代码运行良好。但现在它向我显示了一个错误。我遇到了关于const createStoreWithMiddleware = applyMiddleware(ReduxPromise)(createStore);的问题

如何通过这个中间件使用 store 以及如何传入<Provider> 标签的 store 属性？

Answer 1

我建议你使用redux-persist。

坚持并补充一个 redux 存储

使用此中间件，您在 Redux Store 中的所有数据将自动持久化到 localStorage（也可以使用不同类型的存储）。因此，当您刷新页面时，先前请求中已持久化的数据将自动重新水化（推送）回 Store。

---

示例，取自文档：

配置：

// configureStore.js

import { createStore } from 'redux'
import { persistStore, persistReducer } from 'redux-persist'
import storage from 'redux-persist/lib/storage' // defaults to localStorage for web and AsyncStorage for react-native

import rootReducer from './reducers'

const persistConfig = {
  key: 'root',
  storage,
}

const persistedReducer = persistReducer(persistConfig, rootReducer)

export default () => {
  let store = createStore(persistedReducer)
  let persistor = persistStore(store)
  return { store, persistor }
}

用法：

import { PersistGate } from 'redux-persist/integration/react'

// ... normal setup, create store and persistor, import components etc.

const App = () => {
  return (
    <Provider store={store}>
      <PersistGate loading={null} persistor={persistor}>
        <RootComponent />
      </PersistGate>
    </Provider>
  );
};