在 Redux 应用程序中写入 localStorage 的位置？

Question

我想将我的状态树的某些部分保存到 localStorage。这样做的合适地点是什么？减速器还是动作？

Answer 1

一句话：中间件

查看 redux-persist。或者自己写。

_{[2016 年 12 月 18 日更新] 编辑删除了两个类似项目的提及现在不活动或弃用。}

Answer 2

Reducer 永远不是执行此操作的合适位置，因为 reducer 应该是纯净的并且没有副作用。

我建议只在订阅者中执行此操作：

store.subscribe(() => {
  // persist your state
})

在创建商店之前，阅读那些持久化的部分：

const persistedState = // ...
const store = createStore(reducer, persistedState)

如果您使用 combineReducers()，您会注意到未收到状态的 reducer 将使用其默认的 state 参数值正常“启动”。这可能非常方便。

建议您对订阅者进行去抖动处理，以免写入 localStorage 的速度过快，否则会出现性能问题。

最后，您可以创建一个封装它的中间件作为替代方案，但我会从订户开始，因为它是一个更简单的解决方案并且可以很好地完成工作。

Answer 3

要填写 Dan Abramov 的答案，您可以使用 store.subscribe()，如下所示：

store.subscribe(()=>{
  localStorage.setItem('reduxState', JSON.stringify(store.getState()))
})

在创建商店之前，检查 localStorage 并像这样解析您的密钥下的任何 JSON：

const persistedState = localStorage.getItem('reduxState') 
                       ? JSON.parse(localStorage.getItem('reduxState'))
                       : {}

然后将此 persistedState 常量传递给 createStore 方法，如下所示：

const store = createStore(
  reducer, 
  persistedState,
  /* any middleware... */
)

Answer 4

如果有人对上述解决方案有任何疑问，您可以自己写信给。让我告诉你我做了什么。忽略saga middleware的东西只关注两个东西localStorageMiddleware和reHydrateStore的方法。 localStorageMiddleware 拉取所有 redux state 并将其放入 local storage 并且 rehydrateStore 将所有 applicationState 拉入本地存储（如果存在）并将其放入 redux store

import {createStore, applyMiddleware} from 'redux'
import createSagaMiddleware from 'redux-saga';
import decoristReducers from '../reducers/decorist_reducer'

import sagas from '../sagas/sagas';

const sagaMiddleware = createSagaMiddleware();

/**
 * Add all the state in local storage
 * @param getState
 * @returns {function(*): function(*=)}
 */
const localStorageMiddleware = ({getState}) => { // <--- FOCUS HERE
    return (next) => (action) => {
        const result = next(action);
        localStorage.setItem('applicationState', JSON.stringify(
            getState()
        ));
        return result;
    };
};


const reHydrateStore = () => { // <-- FOCUS HERE

    if (localStorage.getItem('applicationState') !== null) {
        return JSON.parse(localStorage.getItem('applicationState')) // re-hydrate the store

    }
}


const store = createStore(
    decoristReducers,
    reHydrateStore(),// <-- FOCUS HERE
    applyMiddleware(
        sagaMiddleware,
        localStorageMiddleware,// <-- FOCUS HERE 
    )
)

sagaMiddleware.run(sagas);

export default store;

Answer 5

我无法回答@Gardezi，但基于他的代码的选项可能是：

const rootReducer = combineReducers({
    users: authReducer,
});

const localStorageMiddleware = ({ getState }) => {
    return next => action => {
        const result = next(action);
        if ([ ACTIONS.LOGIN ].includes(result.type)) {
            localStorage.setItem(appConstants.APP_STATE, JSON.stringify(getState()))
        }
        return result;
    };
};

const reHydrateStore = () => {
    const data = localStorage.getItem(appConstants.APP_STATE);
    if (data) {
        return JSON.parse(data);
    }
    return undefined;
};

return createStore(
    rootReducer,
    reHydrateStore(),
    applyMiddleware(
        thunk,
        localStorageMiddleware
    )
);

不同之处在于我们只是保存了一些动作，您甚至可以使用去抖动功能来仅保存状态的最后一次交互

Answer 6

我来晚了一点，但我根据此处所述的示例实现了持久状态。如果您只想每 X 秒更新一次状态，这种方法可能对您有所帮助：

定义一个包装函数

let oldTimeStamp = (Date.now()).valueOf()
const millisecondsBetween = 5000 // Each X milliseconds
function updateLocalStorage(newState)
{
    if(((Date.now()).valueOf() - oldTimeStamp) > millisecondsBetween)
    {
        saveStateToLocalStorage(newState)
        oldTimeStamp = (Date.now()).valueOf()
        console.log("Updated!")
    }
}

在您的订阅者中调用包装函数

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

在此示例中，状态每 5 秒最多更新一次，无论触发更新的频率如何。

Answer 7

基于其他答案（和 Jam Creencia's Medium article）中提供的优秀建议和简短代码摘录，这里有一个完整的解决方案！

我们需要一个包含 2 个函数的文件，save/load 状态 to/from 本地存储：

// FILE: src/common/localStorage/localStorage.js

// Pass in Redux store's state to save it to the user's browser local storage
export const saveState = (state) =>
{
  try
  {
    const serializedState = JSON.stringify(state);
    localStorage.setItem('state', serializedState);
  }
  catch
  {
    // We'll just ignore write errors
  }
};



// Loads the state and returns an object that can be provided as the
// preloadedState parameter of store.js's call to configureStore
export const loadState = () =>
{
  try
  {
    const serializedState = localStorage.getItem('state');
    if (serializedState === null)
    {
      return undefined;
    }
    return JSON.parse(serializedState);
  }
  catch (error)
  {
    return undefined;
  }
};

这些函数由 store.js 导入，我们在其中配置我们的商店：

注意：您需要添加一个依赖项：npm install lodash.throttle

// FILE: src/app/redux/store.js

import { configureStore, applyMiddleware } from '@reduxjs/toolkit'

import throttle from 'lodash.throttle';

import rootReducer from "./rootReducer";
import middleware from './middleware';

import { saveState, loadState } from 'common/localStorage/localStorage';


// By providing a preloaded state (loaded from local storage), we can persist
// the state across the user's visits to the web app.
//
// READ: https://redux.js.org/recipes/configuring-your-store
const store = configureStore({
 reducer: rootReducer,
 middleware: middleware,
 enhancer: applyMiddleware(...middleware),
 preloadedState: loadState()
})


// We'll subscribe to state changes, saving the store's state to the browser's
// local storage. We'll throttle this to prevent excessive work.
store.subscribe(
 throttle( () => saveState(store.getState()), 1000)
);


export default store;

store 被导入到 index.js 中，因此它可以传递到包装 App.js 的 Provider 中:

// FILE: src/index.js

import React from 'react'
import { render } from 'react-dom'
import { Provider } from 'react-redux'

import App from './app/core/App'

import store from './app/redux/store';


// Provider makes the Redux store available to any nested components
render(
 <Provider store={store}>
  <App />
 </Provider>,
 document.getElementById('root')
)

请注意，绝对导入需要将此更改为 YourProjectFolder/jsconfig。json - 这会告诉它在找不到文件时去哪里寻找文件首先。否则，您会看到有关尝试从 src.

外部导入内容的投诉

{
  "compilerOptions": {
    "baseUrl": "src"
  },
  "include": ["src"]
}

Answer 8

如果您不需要将所有 redux 存储复制到 localStorage，您可以使用特定的存储参数：

store.subscribe(()=>{
  window.localStorage.setItem('currency', store.getState().lang)
})

并设置初始状态参数值，如：

const initialState = {
  currency: window.localStorage.getItem('lang') ?? 'en',
}

在这种情况下，您不需要将 const persistedState 传递给 const store = createStore()

Answer 9

我一直在寻找关于如何使用 redux-toolkit-persist 将状态持久化到本地存储的完整示例，但没有成功，直到我遇到上面的 @canProm 响应来解决我的问题。这就是对我有用的

//package.json
 "reduxjs-toolkit-persist": "^7.0.1",
"lodash": "^4.17.21"

 //localstorage.ts
 import localStorage from 'reduxjs-toolkit-persist/es/storage';
  export const saveState = (state: any) => {
  try {
     console.log(state);
     const serializableState = JSON.stringify(state);
     localStorage.setItem('globalState', serializableState);
   } catch (err) {
    console.log('Redux was not able to persist the state into the localstorage');
 }
};


export const loadState = () => {
  try {
    const serializableState: string | any = 
 localStorage.getItem('globalState');
    return serializableState !== null || serializableState === undefined ? JSON.parse(serializableState) : undefined;
   } catch (error) {
      return undefined;
  }
};



//slices - actions
//reduxjs-toolkit-slices.ts
  import { combineReducers, createSlice, PayloadAction } from '@reduxjs/toolkit';
  import { UserModel } from '../model/usermodel';
  import { GlobalState } from './type';

  const deaultState: GlobalState = {
       counter: 0,
       isLoggedIn: false
  };

 const stateSlice = createSlice({
    name: "state",
   initialState: deaultState,
reducers: {
    isLoggedIn: (state, action: PayloadAction<boolean>) => {
        console.log('isLogged');
        console.log(state.isLoggedIn);
        console.log(action);
        state.isLoggedIn = action.payload;
        console.log(state.isLoggedIn);
    },
    setUserDetails: (state, action: PayloadAction<UserModel>) => {
        console.log('setUserDetails');
        console.log(state);
        console.log(action);
        //state.userContext.user = action.payload;
    }
  }
});

//export actions under slices
export const {
  isLoggedIn: isUserLoggedAction,
  setUserDetails: setUserDetailActions
} = stateSlice.actions;

//TODO: use the optimal way for combining reducer using const
//combine reducer from all slice
export const combineReducer = combineReducers({
   stateReducer: stateSlice.reducer
});

 //storeConfig
  //reduxjs-toolkit-store.ts
 import { configureStore } from '@reduxjs/toolkit';
 import { throttle } from 'lodash';
 import { persistReducer } from 'reduxjs-toolkit-persist';
 import autoMergeLevel2 from 'reduxjs-toolkit-persist/lib/stateReconciler/autoMergeLevel2';
 import storage from 'reduxjs-toolkit-persist/lib/storage';
  import { loadState, saveState } from './localStorage';
 import { combineReducer } from './reduxjs-toolkit-slices';

  // persist config
  const persistConfig = {
      key: 'root',
      storage: storage,
      stateReconciler: autoMergeLevel2,
  };
  const persistedReducer = persistReducer(persistConfig, combineReducer);

  // export reducers under slices
  const store = configureStore({
      reducer: persistedReducer,
     devTools: process.env.NODE_ENV !== 'production',
     preloadedState: loadState(), //call loadstate method to initiate store from localstorage
     middleware: (getDefaultMiddleware) =>
        getDefaultMiddleware({
        thunk: true,
        serializableCheck: false,
    }),
 });
 // handle state update event. Whenever the state will change, this subscriber will call the saveState methode to update and persist the state into the store
store.subscribe(throttle(() => {
    saveState(store.getState());
 }, 1000));


export default store;

 //App.ts
 import { persistStore } from 'reduxjs-toolkit-persist';
 import { PersistGate } from 'reduxjs-toolkit-persist/integration/react';
 import './i18n';

 let persistor = persistStore(store);

  ReactDOM.render(
     <Provider store={store}>
       <PersistGate loading={<div>Loading .....</div>} persistor={persistor}>
         <HalocarburesRouter />
       </PersistGate>
     </Provider>,
   document.getElementById('ingenierieMdn'));

在 Redux 应用程序中写入 localStorage 的位置？

Where to write to localStorage in a Redux app?

javascript

state

local-storage

redux