这是我为一个项目构建的一个教育组件。目前,教育数据是在第二次重新渲染时从 redux 状态中读取的。我的目标是为教育数据中的每个单独条目添加一个可见性按钮。Education_data 是一个对象数组。该按钮将允许用户隐藏链接到他们希望隐藏的索引的数据。我有另一个名为education_vis 的变量,它存储了一个大小为education_data 大小的数组,最初具有真实值,需要将其保存到状态中以隐藏渲染上的元素。使用 useState 进行的这种保存与从使用 useSelector 抓取的 redux 数据中读取的数据不同步。
import React, { useEffect, useState } from 'react';
import { useDispatch, useSelector } from "react-redux";
import * as educationActions from "../../actions/educationActions";
import DeleteButton from "./deleteButton";
import UpdateButton from "./updateButton";
import VisibilityOffIcon from '@material-ui/icons/VisibilityOff';
import { BrowserRouter as Router, Switch, Route, Link } from "react-router-dom";
import EducationForm from "../forms/updateForms/educationForm";
const Education = () => {
const dispatch = useDispatch();
useEffect(() => {
const userEducation = async () => {
await dispatch(educationActions.getEducation('60fcc884bbed863d20b02573'));
};
userEducation();
}, [dispatch]);
const education_data = useSelector((state) => state.education.education);
var education_vis = Array(education_data.length);
if(education_vis[0] === undefined){
for(var i = 0; i < education_data.length; i++){
education_vis[i] = true;
}
}
const handleChange = (index) => {
education_vis[index] = !education_vis[index];
console.log(education_vis);
}
return (
<Router>
<div>
<p> Education </p>
<hr />
{education_data.map((value, index) => {
return (
<div>
<VisibilityOffIcon onClick = {()=>handleChange(index)} />
{education_vis[index] ? <div key={index}>
<p>{ value.university_name }, { value.university_city }, { value.university_state } { value.month_begin } { value.year_begin } - { value.month_end } { value.year_end }</p>
<p>{ value.degree_name } in { value.domain_name } { value.GPA }</p>
<DeleteButton elementId = { value._id } page = { "Education" }/>
<Link to={ `/education/${value._id}/update` } ><UpdateButton /></Link>
</div> : null}
</div>
)
})}
</div>
<Switch>
<Route path="/education/:elementId/update">
<EducationForm />
</Route>
</Switch>
</Router>
)
}
export default Education
以下是示例 education_data 的外观。相同的education_vis 将是[true, true]
/* var education_data = [
{
degree_name: "Masters",
domain_name: "Information Sciences and Technology",
school_name: "iSchool",
university_name: "Rochester Institute of Technology",
university_city: "Rochester",
university_state: "NY",
university_country: "USA",
year_begin: "2019",
month_begin: "August",
year_end: "2021",
month_end: "December",
GPA: "3.8",
},{
degree_name: "Bachelors",
domain_name: "CS",
school_name: "DSCE",
university_name: "VTU",
university_city: "Bangalore",
university_state: "Karnataka",
university_country: "India",
year_begin: "2014",
month_begin: "August",
year_end: "2018",
month_end: "June",
GPA: "3.8",
}] */
这是我尝试使用 useStates() 设置状态的方法。
const [educationVisibility, setEducationVisibility] = useState(education_vis);
useEffect(() => {
setEducationVisibility(education_vis)
},[education_vis])
我试图在单击 . 为此,我需要将education_vis 上传到能够重新渲染组件的状态,并且需要帮助来完成此操作。
education_vis
当你这样做时,你正在变异education_vis[index] === !education_vis[index]
。所以现在useEffect
不会触发,因为education_vis
从来没有改变过。它刚刚发生了变异,因此对象的引用仍然相同。
React 本质上使用Object.is
依赖项来比较依赖项值,因此它将返回 false,因此其中的代码useEffect
将不会运行。
另外,我看到您useEffect
为此使用了 a但您不需要,因为您已经有了handleChange
回调。您可以从那里更新状态。
const [educationVisibility, setEducationVisibility] = useState(education_vis);
const handleChange = (index) => {
education_vis[index] = !education_vis[index];
setEducationVisibility([...education_vis]); // using spread to get a new instance of the array
}
您还可以使用immer库来帮助您完成其中的一些操作。但就是说,如果你真的需要它。当您拥有复杂的数据结构时,它确实有帮助。
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我来说两句