等待反应上下文后组件不重新渲染答案

【问题标题】：Component not re-rendering after waiting for react context等待反应上下文后组件不重新渲染
【发布时间】：2021-01-29 01:43:33
【问题描述】：

我正在检查 isFetchingData 是否还没有渲染，但是一旦 isFetchingData 设置为 false，它就不会重新渲染。我在上下文中有 useEffect，我希望一旦将 isFetchingData 设置为 false，它会重新渲染。有什么想法吗？

当我刷新页面时，它会使用数据呈现。所以我认为它与重新渲染有关。

我正在使用反应上下文来获取数据并公开函数来过滤该数据并得到我需要的东西。

上下文：

import React, { useEffect, useState } from 'react';
import getAllEmployees from 'my-services/employee/getAllEmployees';
import { arrayOf, node, oneOfType } from 'prop-types';

export const EmployeeContext = React.createContext({
    allEmployees: [],
    getActiveEmployees: () => [],
    getTerminatedEmployees: () => []
});

const EmployeesProvider = ({ children }) => {
    const [isFetchingData, setIsFetchingData] = useState(true);
    const [allEmployees, setAllEmployees] = useState({});

    useEffect(() => {
        getAllEmployees().then(
            //doing something
        ).then(employees => {
            setAllEmployees(employees);
            setIsFetchingData(false);
        });
    }, [isFetchingData])


    const context = {
        isFetchingData,
        allEmployees,
        getActiveEmployees: () =>
            allEmployees.filter(x => x.status === 'Current'),

        getTerminatedEmployees: () =>
            allEmployees.filter(x => x.status === 'Terminated')
    };

    return (
        <EmployeeContext.Provider value={context}>{children}</EmployeeContext.Provider>
    );
};

EmployeesProvider.propTypes = {
    children: oneOfType([node, arrayOf(node)])
};
EmployeesProvider.defaultProps = {
    children: undefined
};

export default EmployeesProvider;

组件：

import React, { useContext } from 'react';
import styled from 'styled-components';
import { EmployeeContext } from 'my-contexts/EmployeeContext';
import EmployeeCard from '../../../components/EmployeeCard';


const EmployeesTab = () => {

    const {
        getActiveEmployees,
        getTerminatedEmployees,
        isFetchingData
    } = useContext(EmployeeContext);

    let activeEmployees = [];
    let terminatedEmployees = [];

    if (!isFetchingData) { 
        activeEmployees = getActiveEmployees(); 
        terminatedEmployees = getTerminatedEmployees();
    }

    if(isFetchingData) {
        return <p>Loading</p>;
    }

    return (
        <Outer>
            <TopHeader>
                <H3>Employees ({activeEmployees.length})</H3>
            </TopHeader>

            <Wrapper>
                {activeEmployees.map(employee => {
                    return (
                        <EmployeeCard
                            id={employee.id}
                            guid={employee.guid}
                            firstName={employee.name.first}
                            lastName={employee.name.last}
                            jobTitle={employee.jobTitle}
                        />
                    );
                })}
            </Wrapper>

            <H3>Terminated employees({terminatedEmployees.length})</H3>
            <Wrapper>
                {terminatedEmployees.map(employee => {
                    return (
                        <EmployeeCard
                            id={employee.id}
                            guid={employee.guid}
                            firstName={employee.name.first}
                            lastName={employee.name.last}
                            jobTitle={employee.jobTitle}
                        />
                    );
                })}
            </Wrapper>
        </Outer>
    );
};

export default EmployeesTab;

【问题讨论】：

标签： javascript reactjs react-context

【解决方案1】：

我认为可能存在很多问题。
首先，请检查整个组件是否被上下文提供者关闭。
例如

<EmployeesProvider>
  <EmployeesTab/>
<EmployeesProvider/>

请检查这个问题。

【讨论】：