使用redux-saga中间件实现异步数据请求

概述：

react-saga有3个重要的函数:call ,put takeEvery。

• call:在worker saga里执行异步函数；
• put:异步函数有结果的时候，派发action；
• takeEvery:当监听到aciton时,执行worker saga。

saga主要用到的是generator。

使用：

新建sagas.js

import { takeEvery , put} from 'redux-saga/effects'
import axios from 'axios';
import { GET_INIT_LIST } from './actionType';
import { initListAction} from './actionCreator';
//worker saga
function* todolist() {
    //异步获取数据
    try{
        const res = yield  axios.get('api/list');
        const action=initListAction(res.data);
        yield put(action);
    }catch(e){
        console.log('list.json 网络请求失败')
    }
}
//当type为GET_INIT_LIST的action触发时，调用todolist函数
function* mySaga() {
  yield takeEvery(GET_INIT_LIST, todolist);
}

export default mySaga;

创建store的时候，按照文档配置好redux-saga

import { createStore, applyMiddleware ,compose} from 'redux';
import reducer from './reducer'
import createSagaMiddleware from 'redux-saga'
import mySaga from './sagas'
//1.创建中间件
const sagaMiddleware = createSagaMiddleware();
//2.应用中间件
const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ ?   window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__({}) : compose;
const enhancer = composeEnhancers(applyMiddleware(sagaMiddleware));
const store = createStore(reducer, enhancer);
//3.执行run
sagaMiddleware.run(mySaga)
export default store;

　组件里还是和之前一样

componentDidMount(){
	const action=getInitListAction();
	store.dispatch(action);
}