TypeError：无法读取未定义的属性“用户”|但用户已定义
Posted
技术标签:
【中文标题】TypeError：无法读取未定义的属性“用户”|但用户已定义【英文标题】：TypeError: Cannot read property 'users' of undefined | but users is defined 【发布时间】：2021-10-21 04:56:16 【问题描述】：我现在遇到这个错误，我不知道为什么。
我知道错误行在此代码中，但我看不出我做错了什么。
const found = getState().usersState.users.some(el => el.uid === uid);
代码：
import USER_STATE_CHANGE, USER_POSTS_STATE_CHANGE, USER_FOLLOWING_STATE_CHANGE, USERS_DATA_STATE_CHANGE from "../constants/index";
import firebase from "firebase/app";
import 'firebase/firestore'
export function fetchUser()
return ((dispatch) =>
firebase.firestore()
.collection("users")
.doc(firebase.auth().currentUser.uid)
.get()
.then((snapshot) =>
if(snapshot.exists)
dispatch(type: USER_STATE_CHANGE, currentUser: snapshot.data)
else
console.log('does not exist')
)
)
export function fetchUserPosts()
return ((dispatch) =>
firebase.firestore()
.collection("posts")
.doc(firebase.auth().currentUser.uid)
.collection("userPosts")
.orderBy("creation", "asc")
.get()
.then((snapshot) =>
let posts = snapshot.docs.map(doc =>
const data = doc.data();
const id = doc.id;
returnid, ...data
)
dispatch(type: USER_POSTS_STATE_CHANGE, posts)
)
)
export function fetchUserFollowing()
return ((dispatch) =>
firebase.firestore()
.collection("following")
.doc(firebase.auth().currentUser.uid)
.collection("userFollowing")
.onSnapshot((snapshot) =>
let following = snapshot.docs.map(doc =>
const id = doc.id;
return id
)
dispatch(type: USER_FOLLOWING_STATE_CHANGE, following)
for(let i = 0; i < following.length; i++)
dispatch(fetchUsersData(following[i]));
)
)
export function fetchUsersData(uid)
return ((dispatch, getState) =>
const found = getState().usersState.users.some(el => el.uid === uid);
if (!found)
firebase.firestore()
.collection("users")
.doc(uid)
.get()
.then((snapshot) =>
if (snapshot.exists)
let user = snapshot.data();
user.uid = snapshot.id;
dispatch( type: USERS_DATA_STATE_CHANGE, user );
else
console.log('does not exist')
)
if(getPosts)
dispatch(fetchUsersFollowingPosts(uid));
)
export function fetchUsersFollowingPosts(uid)
return ((dispatch, getState) =>
firebase.firestore()
.collection("posts")
.doc(uid)
.collection("userPosts")
.orderBy("creation", "asc")
.get()
.then((snapshot) =>
const uid = snapshot.query.EP.path.segments[1];
const user = getState().usersState.users.find(el => el.uid === uid);
let posts = snapshot.docs.map(doc =>
const data = doc.data();
const id = doc.id;
return id, ...data, user
)
for(let i = 0; i< posts.length; i++)
dispatch(fetchUsersFollowingLikes(uid, posts[i].id))
dispatch( type: USERS_POSTS_STATE_CHANGE, posts, uid )
)
)
这是我在 reducers 文件夹中的内容：
index.js：
import combineReducers from 'redux'
import user from './user'
import users from './users'
const Reducers = combineReducers(
userState: user,
userState: users
)
export default Reducers
user.js:
import USER_STATE_CHANGE, USER_POSTS_STATE_CHANGE, USER_FOLLOWING_STATE_CHANGE from "../constants"
const initialState =
currentUser: null,
posts: [],
follwing: [],
export const user = (state = initialState, action) =>
switch (action.type)
case USER_STATE_CHANGE:
return
...state,
currentUser: action.currentUser
case USER_POSTS_STATE_CHANGE:
return
...state,
posts: action.posts
case USER_FOLLOWING_STATE_CHANGE:
return
...state,
following: action.following
default:
return state
users.js：
import USERS_POSTS_STATE_CHANGE, USERS_DATA_STATE_CHANGE from "../constants"
const initialState =
users: null,
userLoaded: 0,
export const users = (state = initialState, action) =>
switch (action.type)
case USERS_DATA_STATE_CHANGE:
return
...state,
users: [...state.users, action.users]
case USERS_POSTS_STATE_CHANGE:
return
...state,
usersLoaded: state.userLoaded + 1,
users: state.users.map(user => user.uid === action.uid ?...user, posts: action.posts :
user)
default:
return state
【问题讨论】：
请出示您的减速机 你必须先提供你的 reducer，然后才能有人帮忙，因为user state 是在你的 reducer 中定义的。
@Viet 已上传，希望对您有所帮助！
@Delice 希望这会有所帮助！
【参考方案1】：
问题就在这里：
const found = getState().usersState.users.some(el => el.uid === uid);
这里的users 来自异步请求，在第一次渲染时不可用。因此，您必须进行如下检查：
if( getState().usersState && getState().usersState.users ) // Access it when it is available
const found = getState().usersState.users.some(el => el.uid === uid);
或
const found = ( getState().usersState && getState().usersState.users ) ? getState().usersState.users.some(el => el.uid === uid): [];
类似的东西。试试这个，错误就会消失，你会得到数据。
【讨论】：
谢谢@Mayank！我不得不使用你的和 Viets 他的，现在它正在工作！谢谢！ 请将getState().usersState 提取到变量中。这对我来说太多了
@Delice 对，最好将它存储在一个变量中，并在所有需要它的地方使用该变量。【参考方案2】：
也许 firebase 仍在获取用户，您可以使用可选链接 ? 来保护这种行为。试试这个
const found = getState().usersState?.users?.some(el => el.uid === uid);
【讨论】：
【参考方案3】：您在combineReducers 中写错了。 usersState 而不是 userState
const Reducers = combineReducers(
userState: user,
usersState: users
)
【讨论】：
...或者他拼错了他的状态：D @Delice 是她哈哈 @Viet 这有帮助，但我不得不将您的答案与 Mayank 他的答案结合起来，然后它就奏效了！谢谢！ :)以上是关于TypeError：无法读取未定义的属性“用户”|但用户已定义的主要内容，如果未能解决你的问题，请参考以下文章
如何在 ReactStrap 中使用 innerRef ？ #TypeError：无法读取未定义的属性“用户名”
TypeError：无法读取未定义 Firebase 存储反应的属性“参考”
错误：TypeError：尝试为网站 node.js 注册用户时无法读取未定义的属性“catch”
TypeError：无法读取 Vue 中未定义的属性“id”