更新存储后，React 中的 useEffect 不更新组件 [英] useEffect in React not update component after update store

问题描述

我不明白为什么 React 不更新我的对象.在另一个组件中通过调度更新状态.在此(在下面的代码中)中，mapStateToProps 类别中的代码正在更改(控制台日志显示另外一个类别).但是组件没有重新渲染，虽然在 useEffect 的组件中我使用了 props.categories.元素中的事件 console.log 不运行

const LeftSidebar = (props: any) =>{console.log('props.categories 改变后不渲染')useEffect(() => {props.dispatch(getCategories())}, [props.categories]);const addCategoryHandler = (categoryId: number) =>{props.history.push('/category/create/' + categoryId)};返回 (<div className='left-sidebar'><标志/><MenuSidebar category={props.categories} onClickAddCategory={addCategoryHandler}/>

);};函数 mapStateToProps(state: State) {const 类别 = state.category &&状态.类别.列表；console.log('这个类别改变了，但 LeftSidebar 没有改变')控制台日志(类别)返回{类别}；}导出默认连接(mapStateToProps)(LeftSidebar)；

我想如果我更新状态，则根据此状态响应更新组件.它应该如何工作?它应该如何工作?可能有用，添加类别的项目不是父或子，而是邻居我的减速机

import {CATEGORIES_GET, CATEGORY_CREATE} from "../actions/types";导出默认函数 (state={}, action: any) {开关(动作.类型){案例CATEGORIES_GET:返回 {...状态，列表:action.payload};案例 CATEGORY_CREATE:返回 {...状态，列表:action.payload};默认:返回状态；}}

感谢您解决问题.所有问题都出在不可变数据中.我使用了灯具，没有正确复制数组

import {CATEGORIES_GET, CATEGORY_CREATE} from "./types";从../../fixtureData"导入{categoryMenuItems as items}；从../../types"导入{NewCategory}；让 categoryMenuItems = 项目；//我的错误，我使用了不可变的值.不为状态使用固定装置))让id = 33;导出函数 getCategories() {返回 {类型:CATEGORIES_GET，有效负载:类别菜单项}}导出函数 createCategory(newCategory: NewCategory) {身份证++常量类别 = {标题:newCategory.name，身份证:身份证};//错误我使用相同的数组，而不是像 let clonedCategoryMenuItems = [...categoryMenuItems] 那样克隆categoryMenuItems.push(category);返回 {类型:CATEGORY_CREATE，有效负载:类别菜单项}}

状态不使用fixtures，使用真实的api :)

解决方案

也许你的状态不是一成不变的.在您的减速器中使用扩展运算符添加新项目

<代码>{列表: [...状态.列表，添加类别]}

代替

state.list.push( addedCategory)

I don't understand why React not update my object. In another component through the dispatch I update the state. In this (in code below) code in mapStateToProps categories are changing (console log show one more category). But component not rerender, although in component in useEffect I use props.categories. Event console.log in element does not run

const LeftSidebar = (props: any) => {
    console.log('not render after props.categories changed')
    useEffect(() => {
        props.dispatch(getCategories())
    }, [props.categories]);

    const addCategoryHandler = (categoryId: number) => {
        props.history.push('/category/create/' + categoryId)
    };

    return (
        <div className='left-sidebar'>
            <Logo/>
            <MenuSidebar categories={props.categories} onClickAddCategory={addCategoryHandler}/>
        </div>
    );
};

function mapStateToProps(state: State) {
    const categories = state.category && state.category.list;
    console.log('this categories changes, but LeftSidebar not changing')
    console.log(categories)
    return { categories };
}

export default connect(mapStateToProps)(LeftSidebar);

I thought if i update state, react update components dependent on this state. How should it work? how should it work? It may be useful, the item that adds the category is not a parent or child, it is a neighbor My reducer

import {CATEGORIES_GET, CATEGORY_CREATE} from "../actions/types";

export default function (state={}, action: any) {
    switch (action.type) {
        case CATEGORIES_GET:
            return {...state, list: action.payload};
        case CATEGORY_CREATE:
            return {...state, list: action.payload};
        default: return state;
    }
}

Thanks for solving problem. All problem was in inmutable data. I used fixtures, and not copied properly array

import {CATEGORIES_GET, CATEGORY_CREATE} from "./types";
import {categoryMenuItems as items} from "../../fixtureData";
import {NewCategory} from "../../types";

let categoryMenuItems = items; // My mistake, I used not immutable value. Not use fixtures for state))
let id = 33;

export function getCategories() {
    return {
        type: CATEGORIES_GET,
        payload: categoryMenuItems
    }
}

export function createCategory(newCategory: NewCategory) {
    id++
    const category = {
        title: newCategory.name,
        id: id
    };

    // MISTAKE I use same array, not cloned like let clonedCategoryMenuItems = [...categoryMenuItems]
    categoryMenuItems.push(category);

    return {
        type: CATEGORY_CREATE,
        payload: categoryMenuItems
    }
}

Not use fixtures for state, use real api :)

解决方案

Maybe your state not is inmutable. In your reducer use spread operator to add new items

{
    list: [
       ...state.list,
       addedCategory
    ]
}

Instead of

state.list.push(addedCategory)

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