React Redux 状态在页面刷新时丢失

Question

在我的反应应用程序中，我有 3 个组件。通过一个按钮从第一个组件，我使用链接转到第二个组件。在第 2 次我创建一个状态（redux 存储），对其进行操作，当通过提交按钮完成操作时，我重定向到第 3 个组件。在第三个组件，我也看到了状态（通过 redux chrome 工具），但是当我刷新页面时（更改和保存代码时的 webpack 事情），我失去了状态并得到一个空对象。

这是我的应用程序的结构。

index.js

const store = createStore(
  rootReducer,
  composeWithDevTools(applyMiddleware(thunk))
);

ReactDOM.render(
  <BrowserRouter>
    <Provider store={store}>
      <Route component={App} />
    </Provider>
  </BrowserRouter>,
  document.getElementById("root")
);

App.js

const App = ({ location }) => (
  <Container>
    <Route location={location} path="/" exact component={HomePage} />
    <Route location={location} path="/GameInit" exact component={GameInit} />
    <Route location={location} path="/Battle" exact component={Battle} />
  </Container>
);

App.propTypes = {
  location: PropTypes.shape({
    pathname: PropTypes.string.isRequired
  }).isRequired
};

export default App;

在主页，我有一个链接到 GameInit 的按钮

const HomePage = () => (<Button color="blue" as={Link} to="/GameInit">START GAME</Button>);
export default HomePage;

GameInit 页面看起来像

class GameInit extends Component {
  componentWillMount() {
    const { createNewPlayer} = this.props;
    createNewPlayer();
  }
/* state manipulation till it gets valid */
 palyerIsReady()=>{ history.push("/Battle");}

export default connect(mapStateToProps,{ createNewPlayer})(GameInit);

最后是我第一次看到状态但在刷新时丢失的战斗组件

class Battle extends Component {
  render() {return (/*some stuff*/);}}

Battle.propTypes = {
  players: PropTypes.object.isRequired // eslint-disable-line
};
const mapStateToProps = state => ({
  players: state.players
});
export default connect(mapStateToProps,null)(Battle);

Answer 1

您可以使用redux-persist 之类的东西将redux 状态保存到local storage 或 到另一个存储系统。

Answer 2

您可以轻松地将其保存在本地存储中。检查下面的示例。

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

const saveState = (state) => {
  try {
    const serializedState = JSON.stringify(state);
    localStorage.setItem('state', serializedState);
  } catch (e) {
    // Ignore write errors;
  }
};

const peristedState = loadState();

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

const store = createStore(
  persistedState,
  // Others reducers...
);

render(
  <Provider store={store}>
    <App/>
  </Provider>,
  document.getElementById('root');
);

---

序列化是一项昂贵的操作。您应该使用限制功能（如 lodash 实现的功能）来限制保存次数。

例如：

import throttle from 'lodash/throttle';

store.subscribe(throttle(() => {
  saveState(store.getState());
}, 1000));

Answer 3

我个人对热重载的建议是使用这个：React hot loader，这可以防止页面重载并且只切换出改变的块。这意味着您的状态在开发时永远不会丢失。

它很容易安装。您只需添加一个条目并将您的初始组件包装在 hot 中，您可以从包中获取它。

如果您需要有关其工作原理的更多信息，我建议您观看创作者的this talk。

Answer 4

    import React from "react";
import ReactDOM from "react-dom";
import "./index.css";
import * as serviceWorker from "./serviceWorker";
import { Provider } from "react-redux";
import { store } from "./rootReducer";
import { BrowserRouter } from "react-router-dom";

if (process.env.NODE_ENV === "development" && module.hot) {
  module.hot.accept("./rootReducer", () => {
    const newRootReducer = require("./rootReducer").default;
    store.replaceReducer(newRootReducer);
  });
}

export type AppDispatch = typeof store.dispatch;

const render = () => {
  const App = require("./App").default;
  ReactDOM.render(
    <Provider store={store}>
      <BrowserRouter>
        <App />
      </BrowserRouter>
    </Provider>,
    document.getElementById("root"),
  );
};

render();

if (process.env.NODE_ENV === "development" && module.hot) {
  module.hot.accept("./App", render);
}

Answer 5

Alexender Annic 正确回答：

// persist store code
const loadState = () => {
  try {
    const serializedState = localStorage.getItem('state');
    if(serializedState === null) {
      return undefined;
    }
    return JSON.parse(serializedState);
  } catch (e) {
    return undefined;
  }
};

const saveState = (state) => {
  try {
    const serializedState = JSON.stringify(state);
    localStorage.setItem('state', serializedState);
  } catch (e) {
    // Ignore write errors;
  }
};

const persistedState = loadState();

// This persistedState is includedat the time of store creation as initial value
const store = createStore(reducers, persistedState);

// This is actually call every time when store saved
store.subscribe(() => {
  saveState(store.getState());
});


export default store;