redux及react-redux都只能实现数据的同步修改更新，有点类似于vue中的mutation，只能做同步操作，异步的话不用actions来实现。由于在项目始终不可避免要实现的异步数据的更新，这明显不够用了。是时候引入我们的异步中间件redux-thunk了
实现效果
代码实现
- 安装
redux-thunk
npm i redux-thunk
- store/index.js
import { createStore, applyMiddleware, compose } from "redux";
import { combineReducers } from "redux-immutable";
import { thunk } from "redux-thunk";import { CounterReducer } from "./CounterReducer";const reducers = combineReducers({count: CounterReducer,
});
const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ || compose;const store = createStore(reducers, composeEnhancers(applyMiddleware(thunk)));export default store;
- CounterReducer.js
封装了两个异步方法，模拟数据的异步获取，然后导出供其他组件使用
import { fromJS } from "immutable";
const initialState = fromJS({counter: 0,userInfo: {name: "John Doe",age: 25,},
});
function CounterReducer(state = initialState, action) {console.log("🚀 ~ CounterReducer ~ action:", action);switch (action.type) {case "ADD":return state.update("counter", (val) => {return val + 1;});case "ADD_TWO":return state.update("counter", (val) => {return val + 2;});case "DEC":return state.update("counter", (val) => val - 1);case "DEC_TWO":return state.update("counter", (val) => val - 2);case "CHANGE_NAME":return state.setIn(["userInfo", "name"], action.payload);default:return state;}
}// async action 2s later
function handleDelayAdd() {return (dispatch) => {// 模拟异步接口setTimeout(() => dispatch({ type: "ADD_TWO" }), 2000);};
}// async action 2s later
function handleDelayReduce() {return (dispatch) => {// 模拟异步接口setTimeout(() => dispatch({ type: "DEC_TWO" }), 2000);};
}export { CounterReducer, handleDelayAdd, handleDelayReduce };
- DemoB.js
引入两个异步的方法，注意跟同步的dispatch使用方法有点区别，dispatch(handleDelayAdd())在dispatch直接调用了该方法
import { useSelector, useDispatch } from "react-redux";
import { Button, Space, Divider } from "antd";
import { handleDelayAdd, handleDelayReduce } from "../../store/CounterReducer";
function DemoB() {const count = useSelector((state) => state.getIn(["count", "counter"]));const userInfo = useSelector((state) => state.getIn(["count", "userInfo"]));const dispatch = useDispatch();return (<div><p>Demo B</p><div><Space split={<Divider />}><span>name: {userInfo.get("name")}</span><span>age: {userInfo.get("age")}</span><span>count:{count}</span></Space></div><Space><Button type="primary" onClick={() => dispatch({ type: "ADD" })}>add count</Button><Button type="primary" danger onClick={() => dispatch({ type: "DEC" })}>minus count</Button><Button type="primary" onClick={() => dispatch(handleDelayAdd())}>delay 2s add count</Button><Buttontype="primary"dangeronClick={() => dispatch(handleDelayReduce())}>delay 2s minus count</Button><Buttontype="dashed"dangeronClick={() => dispatch({ type: "CHANGE_NAME", payload: "张学友" })}>change name</Button></Space></div>);
}
export default DemoB;
这样我们就实现了在react项目中数据的异步更新。整体还是比较简单的。
总结
在这个具有副作用的action中，我们可以看出，函数内部可能极为复杂。如果需要为每一个异步操作都如此定义一个action，显然action不易维护。
action不易维护的原因：
- action的形式不统一
- 就是异步操作太为分散，分散在了各个action中