[英]Fetch data with redux saga
我创建了一个示例,用于从使用redux-thunk
API 获取数据。 以下代码正在运行。
在这种情况下,我想重写我的代码,但使用redux saga
。
import React from 'react'; import {createStore, applyMiddleware} from 'redux'; import ReactDOM from "react-dom"; import thunk from 'redux-thunk'; import axios from 'axios'; function App(props) { const initialState = { loading: false, data: [], error: '' }; const reducer = function (state = initialState, action) { switch (action.type) { case 'START_FETCH': return { ...state, loading: true }; case 'PROCESS_FETCH': return { ...state, loading: false, data: action.payload, error: "" }; case 'END_FETCH': return { ...state, loading: false, data: [], error: action.payload } } return state; }; const START_FETCH = 'START_FETCH'; const PROCESS_FETCH = 'PROCESS_FETCH'; const END_FETCH = 'END_FETCH'; let startFetchFun = () => { return { type: START_FETCH, loading: true } }; let processFetchFun = (users) => { return { type: PROCESS_FETCH, payload: users } }; let endFetchFun = (error) => { return { type: PROCESS_FETCH, payload: error } }; let fetchUsersWithThunk = () => { return function (dispatch) { dispatch(startFetchFun()); axios.get('https://jsonplaceholder.typicode.com/users') .then((response) => { dispatch(processFetchFun(response.data)); }) .catch((error) => { dispatch(endFetchFun(error.message)); console.log(error.message); }) } }; const store = createStore(reducer, applyMiddleware(thunk)); store.subscribe(() => { console.log(store.getState()) }); store.dispatch(fetchUsersWithThunk()); return ( <div className="main"> <h1>Redux-Thunk</h1> </div> ); } ReactDOM.render( <App/>, document.getElementById('root'));
我想使用 redux saga 编写上面的代码,以更好地理解 saga。 那么,如何在这个例子中使用 redux-saga 呢? 谁能帮助我?
Redux Saga 使用yield call
像 API 服务一样调用 promise,并使用yield put
将操作分派到 store。
区别在于阻塞和不阻塞调用。 因为我们想等待服务器响应我们的请求,所以我们将使用作为阻塞函数的yield call
。 使用yield put({ type: "actionName" })
代替直接在 generator saga 内分派动作。 这对于测试目的也很有用。
所以你应该写你的传奇如下:
import {all, fork, put, call, takeLatest} from 'redux-saga/effects';
function* handleRequest (action) {
try {
yield put(startFetchFunc()); // dispatch the action to the store.
const result = yiels call(apiService.users, [data to pass]); // wait for the response blocking the code execution.
yield put(processFetchFun(result)); // dispatch the action to the store containing the data
} catch (e) {
yield put(endFetchFun('Error'));
}
}
function* watchRequest() {
yield takeLatest({type: "START_FETCH"}, handleRequest);
}
export function* rootSaga() {
yield all([
fork(wathcRequest),
// ... more watchers will be here...
]);
}
按照此处的说明配置您的存储https://redux-saga.js.org/docs/introduction/BeginnerTutorial.html
我建议您不止一次阅读文档。 它包含许多有用的信息,起初可能会很奇怪,但一旦您了解它的工作原理,就会清楚得多。
您需要配置您的商店以使用 saga 中间件:
import React from 'react';
import createSagaMiddleware from 'redux-saga';
import { createStore, applyMiddleware } from 'redux';
import reducer from './reducers';
import rootSaga from './sagas';
const sagaMiddleware = createSagaMiddleware();
const store = createStore(
reducer,
applyMiddleware(sagaMiddleware, logger),
);
sagaMiddleware.run(rootSaga); // < -- rootSaga exports all sagas in your app
然后你可以将你的 thunk 转换为一个 saga:
import {call} from 'redux-saga/effects';
function* fetchUsersSaga(payload){
try {
yield call(startFetchFun());
axios.get('https://jsonplaceholder.typicode.com/users')
.then((response) => {
yield call(processFetchFun(response.data));
})
} catch(err) {
yield call(endFetchFun(error.message));
console.log(error.message);
}
};
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