React-redux 教程 - TypeError: Cannot read properties of undefined (reading 'map')答案

【问题标题】：React- redux tutorial - TypeError: Cannot read properties of undefined (reading 'map')React-redux 教程 - TypeError: Cannot read properties of undefined (reading 'map')
【发布时间】：2021-12-10 04:20:48
【问题描述】：

我是 react 新手，所以我尝试遵循 react redux 教程并收到此错误 - TypeError: Cannot read properties of undefined (reading 'map')

如果有人能帮忙谢谢你，我真的很感激！

下面是我的代码

    import React, {useState} from 'react'
import { useSelector } from 'react-redux'
import { Link } from 'react-router-dom'


export const PostsList = () => {
const posts = useSelector(state => state.posts)


const renderedPosts = posts.map(posts => (
    <article className="post-excerpt" key={posts.id}>
    <h3>{posts.title}</h3>
    <p className="post-content">{posts.content.substring(0, 100)}</p>
    <Link to={`/posts/${posts.id}`} className="button muted-button">
    View Post
    </Link>
    </article>
))

return (
    <section className="posts-list">
    <h2>Posts</h2>
    {renderedPosts}
    </section>
)
}

【问题讨论】：

标签： reactjs function react-redux

【解决方案1】：

我认为您没有从 useSelector 获得任何价值。我的意思是 posts 变量被初始化为未定义。这就是为什么您收到错误无法读取未定义的属性（读取“地图”）的原因。因为 map 不能在 undefined 上工作。

【讨论】：