状态不变时 Redux 不断重新渲染

Question

我正在制作我的第一个 React-Redux 项目。

我学会了仅在组件状态发生变化时才触发的 React 重新渲染。

可是我现在很迷茫

因为状态没有改变，但组件每 1 到 3 秒重新渲染一次。

我试过 shallowEqual，但没用。

为什么会这样？

// container
import React from 'react';
import { useDispatch, useSelector } from 'react-redux';

import Home from 'presentations/Home';
import * as homeActions from 'modules/home';

const HomeContainer = () => {
    const dispatch = useDispatch();
    const list = useSelector(state => state.home.list);

    dispatch(homeActions.getList());

    console.log(list);

    return (
        <Home
        />
    );
}

export default HomeContainer;

// Redux module
import axios from 'axios';
import { call, put, takeEvery } from 'redux-saga/effects';
import { createAction, handleActions } from 'redux-actions';

function getListAPI() {
    return axios.get('http://localhost:8000/');
}

const GET_LIST         = 'home/GET_LIST';
const GET_LIST_SUCCESS = 'home/GET_LIST_SUCCESS';
const GET_LIST_FAILURE = 'home/GET_LIST_FAILURE';

export const getList = createAction(GET_LIST);

function* getListSaga() {
    try {
        const response = yield call(getListAPI);
        yield put({ type: GET_LIST_SUCCESS, payload: response });
    } catch (e) {
        yield put({ type: GET_LIST_FAILURE, payload: e });
    }
}

const initialState = {
    list: []
};

export function* homeSaga() {
    yield takeEvery('home/GET_LIST', getListSaga);
}

export default handleActions(
    {
        [GET_LIST_SUCCESS]: (state, action) => {
            const temp = action.payload.data;
            return {
                list: temp
            };
        }
    }, initialState
);

Answer 1

您正在功能组件体内调用 dispatch = useDispatch();，它会更新状态 list，这会导致重新渲染，然后执行您的 dispatch = useDispatch();，依此类推。

在 useEffect 中调度您的操作以解决问题

const HomeContainer = () => {
  const dispatch = useDispatch();
  const list = useSelector((state) => state.home.list);
  useEffect(() => { //<---like this
    dispatch(homeActions.getList());
  }, []);

  console.log(list);

  return <Home />;
};

状态不变时 Redux 不断重新渲染

Redux keeps re-rendering when state doesn't change

javascript

reactjs

redux

redux-saga