Javascript 如何在React中的事件后触发效果
我正在构建一个React应用程序,它基本上加载博客帖子,并为每个帖子添加评论 呈现博客文章时,也会获取该博客文章的评论。我还有一个组件,允许提交评论 单击submit按钮时,我希望注释刷新其数据源,并立即显示新注释。 如何向我们的comments组件发送某种事件,告诉它发送另一个获取请求 这个问题的核心似乎是: 我如何习惯性地将事件发送到将触发效果的其他React组件 编辑-一般解决方案:Javascript 如何在React中的事件后触发效果,javascript,reactjs,events,material-ui,Javascript,Reactjs,Events,Material Ui,我正在构建一个React应用程序,它基本上加载博客帖子,并为每个帖子添加评论 呈现博客文章时,也会获取该博客文章的评论。我还有一个组件,允许提交评论 单击submit按钮时,我希望注释刷新其数据源,并立即显示新注释。 如何向我们的comments组件发送某种事件,告诉它发送另一个获取请求 这个问题的核心似乎是: 我如何习惯性地将事件发送到将触发效果的其他React组件 编辑-一般解决方案: 将状态提升到最近的部件 创建包含状态更新函数的回调函数。将此回调作为道具传递给将触发事件的组件。事件发生时
从“React”导入React;
从“react”导入{useState、useEffect、useContext};
从“减价到jsx”导入减价;
从“@material ui/core/Container”导入容器;
从“@material ui/core/Typography”导入排版;
从“/SendComment”导入SendComment;
从“/Comments”导入注释;
从“/URL”导入{POST_URL};
从“./UserContext”导入UserContext;
//从“/CommentListContainer”导入CommentListContainer;
导出默认功能帖子(道具){
const user=useContext(UserContext);
const[post,setPost]=useState({
内容:“”,
评论:[],
});
useffect(()=>{
const UNIQUE_POST_URL=[POST_URL,props.location.state.id].join('/');
const fetchPost=async()=>{
const result=等待获取(唯一的发布URL);
const json=wait result.json();
setPost(json);
};
fetchPost();
},[props.location.state.id]);
返回(
{post.title}
{post.content}
{post.content.length!==0&&(
评论
)}
);
}
SendComment.js组件
从“React”导入React;
从“@material ui/core/TextField”导入TextField;
从“@material ui/core/Grid”导入网格;
从“@material ui/core/Button”导入按钮;
从“@material ui/core/Paper”导入纸张;
从“/URL”导入{COMMENT_SUBMIT_URL};
导出默认函数SendComment(道具){
异步函数handleSubmit(e){
const comment=document.querySelector(“#comment”);
//跳过空评论
如果(comment.value==''){
返回;
}
异步函数sendComment(url){
试一试{
const res=等待获取(url{
方法:“POST”,
正文:JSON.stringify({
comment:comment.value,
users\u id:props.user.users\u id,
posts\u id:props.posts\u id,
}),
标题:{
接受:'application/json',
“内容类型”:“应用程序/json”,
“接受语言”:“en-US”,
},
});
comment.value='';
返回res;
}捕获(e){
控制台日志(e);
}
}
const res=wait sendcoment(COMMENT\u SUBMIT\u URL);
如果(res.ok){
//重新加载我们的评论组件!
//这是我们要发送“事件”的地方
//或者不管解决方案是什么
}
}
返回(
提交
);
}
Comments.js
从“React”导入React;
从“react”导入{useState,useEffect};
从“@material ui/core/List”导入列表;
从“@material ui/core/ListItem”导入ListItem;
从“@material ui/core/ListItemText”导入ListItemText;
从“@material ui/core/ListItemAvatar”导入ListItemAvatar;
从“@material ui/core/Avatar”导入化身;
从“@material ui/core/Divider”导入分隔器;
从“/utils”导入{timeAgo};
从“/URL”导入{COMMENT_URL};
导出默认函数注释(道具){
const[comments,setComments]=useState({
对象:[],
});
useffect(()=>{
异步函数getComments(posts\u id){
const filter=JSON.stringify({
筛选器:[{name:'posts\u id',op:'equals',val:posts\u id}],
});
试一试{
注释\u URL.searchParams.set('q',过滤器);
const res=等待获取(注释URL{
方法:“GET”,
标题:{
接受:'application/json',
“内容类型”:“应用程序/json”,
},
});
const json=await res.json();
setComments(json);
}捕获(e){
控制台日志(e);
}
}
getComments(道具、帖子和id);
},[props.posts_id]);
const commentList=comments.objects.map(comment=>(
));
返回{commentList};
}
此代码目前有效,但新注释仅在重新加载页面时显示,而不是在提交后立即显示。这里有一个想法:
你应该在帖子中对状态变量发表评论
像这样const[comments,setComments]=useState([])代码>
您可以在sendcoment
中收到一个名为onCommentSent
的道具。
在代码中,当发送注释时,执行onCommentSent()代码>
因此,在POST中,当发送注释时,可以重新加载注释的数据,并使用setComments(newData)
将其设置为comments
。
当状态重新加载时,注释将重新蚀刻
一个更好的方法是不要在每个comment POST请求中检索所有注释,您可以动态更新状态变量comments
中的数据,知道下次获取服务器时,注释会出现
希望有帮助 这里有一个想法:
你应该在帖子中对状态变量发表评论
像这样const[comments,setComments]=useState([])代码>
你可以
import React from 'react';
import {useState, useEffect, useContext} from 'react';
import Markdown from 'markdown-to-jsx';
import Container from '@material-ui/core/Container';
import Typography from '@material-ui/core/Typography';
import SendComment from './SendComment';
import Comments from './Comments';
import {POST_URL} from './urls';
import UserContext from './UserContext';
//import CommentListContainer from './CommentListContainer';
export default function Post(props) {
const user = useContext(UserContext);
const [post, setPost] = useState({
content: '',
comments: [],
});
useEffect(() => {
const UNIQUE_POST_URL = [POST_URL, props.location.state.id].join('/');
const fetchPost = async () => {
const result = await fetch(UNIQUE_POST_URL);
const json = await result.json();
setPost(json);
};
fetchPost();
}, [props.location.state.id]);
return (
<div>
<Container>
<Typography
variant="h4"
color="textPrimary"
style={{textDecoration: 'underline'}}>
{post.title}
</Typography>
<Markdown>{post.content}</Markdown>
{post.content.length !== 0 && (
<div>
<Typography variant="h4">Comments</Typography>
<SendComment user={user} posts_id={props.location.state.id} />
<Comments user={user} posts_id={props.location.state.id} />
</div>
)}
</Container>
</div>
);
}
import React from 'react';
import TextField from '@material-ui/core/TextField';
import Grid from '@material-ui/core/Grid';
import Button from '@material-ui/core/Button';
import Paper from '@material-ui/core/Paper';
import {COMMENT_SUBMIT_URL} from './urls';
export default function SendComment(props) {
async function handleSubmit(e) {
const comment = document.querySelector('#comment');
// Skip empty comments
if (comment.value === '') {
return;
}
async function sendComment(url) {
try {
const res = await fetch(url, {
method: 'POST',
body: JSON.stringify({
comment: comment.value,
users_id: props.user.users_id,
posts_id: props.posts_id,
}),
headers: {
Accept: 'application/json',
'Content-Type': 'application/json',
'Accept-Language': 'en-US',
},
});
comment.value = '';
return res;
} catch (e) {
console.log(e);
}
}
const res = await sendComment(COMMENT_SUBMIT_URL);
if (res.ok) {
// Reload our comment component !
// Here is where we want to send our "event"
// or whatever the solution is
}
}
return (
<Grid container justify="space-evenly" direction="row" alignItems="center">
<Grid item xs={8}>
<TextField
id="comment"
fullWidth
multiline
rowsMax="10"
margin="normal"
variant="filled"
/>
</Grid>
<Grid item xs={3}>
<Button variant="contained" color="primary" onClick={handleSubmit}>
Submit
</Button>
</Grid>
</Grid>
);
}
import React from 'react';
import {useState, useEffect} from 'react';
import List from '@material-ui/core/List';
import ListItem from '@material-ui/core/ListItem';
import ListItemText from '@material-ui/core/ListItemText';
import ListItemAvatar from '@material-ui/core/ListItemAvatar';
import Avatar from '@material-ui/core/Avatar';
import Divider from '@material-ui/core/Divider';
import {timeAgo} from './utils';
import {COMMENT_URL} from './urls';
export default function Comments(props) {
const [comments, setComments] = useState({
objects: [],
});
useEffect(() => {
async function getComments(posts_id) {
const filter = JSON.stringify({
filters: [{name: 'posts_id', op: 'equals', val: posts_id}],
});
try {
COMMENT_URL.searchParams.set('q', filter);
const res = await fetch(COMMENT_URL, {
method: 'GET',
headers: {
Accept: 'application/json',
'Content-Type': 'application/json',
},
});
const json = await res.json();
setComments(json);
} catch (e) {
console.log(e);
}
}
getComments(props.posts_id);
}, [props.posts_id]);
const commentList = comments.objects.map(comment => (
<ListItem key={comment.id} alignItems="flex-start">
<ListItemAvatar>
<Avatar alt={comment.users.name} src={comment.users.picture} />
</ListItemAvatar>
<ListItemText
primary={`${comment.users.name} - ${timeAgo(comment.created_at)}`}
secondary={comment.comment}></ListItemText>
<Divider />
</ListItem>
));
return <List>{commentList}</List>;
}
export default function Post(props) {
const user = useContext(UserContext);
const [content, setContent] = useState('')
const [title, setTitle] = useState('')
const [comments, setComments] = useState([])
const onNewComment = useCallback((text) => {
// I'm not sure about your comment structure on server.
// So here you need to create an object that your `Comments` component
// will be able to display and then do `setComments(comments.concat(comment))` down below
const comment = {
comment: text,
users_id: user.users_id,
posts_id: props.location.state.id,
};
async function sendComment(url) {
try {
const res = await fetch(url, {
method: 'POST',
body: JSON.stringify(comment),
headers: {
Accept: 'application/json',
'Content-Type': 'application/json',
'Accept-Language': 'en-US',
},
});
return res;
} catch (e) {
console.log(e);
}
}
const res = await sendComment(COMMENT_SUBMIT_URL);
if (res.ok) {
setComments(comments.concat(comment));
}
}, [comments]);
useEffect(() => {
const UNIQUE_POST_URL = [POST_URL, props.location.state.id].join('/');
const fetchPost = async () => {
const result = await fetch(UNIQUE_POST_URL);
const { content, comments, title } = await result.json();
setContent(content);
setComments(comments);
setTitle(title);
};
fetchPost();
}, [props.location.state.id]);
return (
<div>
<Container>
<Typography
variant="h4"
color="textPrimary"
style={{textDecoration: 'underline'}}>
{title}
</Typography>
<Markdown>{content}</Markdown>
{content.length !== 0 && (
<div>
<Typography variant="h4">Comments</Typography>
<SendComment user={user} onNewComment={onNewComment} />
<Comments user={user} comments={comments} />
</div>
)}
</Container>
</div>
);
}
export default function SendComment(props) {
const [text, setText] = useState('');
const handleSubmit = useCallback(() => {
// Skip empty comments
if (comment.value === '') {
return;
}
if(props.onNewComment) {
props.onNewComment(text);
setText('');
}
}, [props.onNewComment, text]);
return (
<Grid container justify="space-evenly" direction="row" alignItems="center">
<Grid item xs={8}>
<TextField
id="comment"
onChange={setText}
fullWidth
multiline
rowsMax="10"
margin="normal"
variant="filled"
/>
</Grid>
<Grid item xs={3}>
<Button variant="contained" color="primary" onClick={handleSubmit}>
Submit
</Button>
</Grid>
</Grid>
);
}
export default function Comments(props) {
const commentList = props.comments.map(comment => (
<ListItem key={comment.id} alignItems="flex-start">
<ListItemAvatar>
<Avatar alt={comment.users.name} src={comment.users.picture} />
</ListItemAvatar>
<ListItemText
primary={`${comment.users.name} - ${timeAgo(comment.created_at)}`}
secondary={comment.comment}></ListItemText>
<Divider />
</ListItem>
));
return <List>{commentList}</List>;
}
export default function SendComment(props) {
const [comments, setComments] = useState({
objects: [],
});
async function getComments(posts_id) {
const filter = JSON.stringify({
filters: [{name: 'posts_id', op: 'equals', val: posts_id}],
});
try {
COMMENT_URL.searchParams.set('q', filter);
const res = await fetch(COMMENT_URL, {
method: 'GET',
headers: {
Accept: 'application/json',
'Content-Type': 'application/json',
},
});
const json = await res.json();
setComments(json);
} catch (e) {
console.log(e);
}
}
useEffect(() => {
getComments(props.posts_id);
}, [props.posts_id]);
async function handleSubmit(e) {
const comment = document.querySelector('#comment');
// Skip empty comments
if (comment.value === '') {
return;
}
async function sendComment(url) {
try {
const res = await fetch(url, {
method: 'POST',
body: JSON.stringify({
comment: comment.value,
users_id: props.user.users_id,
posts_id: props.posts_id,
}),
headers: {
Accept: 'application/json',
'Content-Type': 'application/json',
'Accept-Language': 'en-US',
},
});
comment.value = '';
return res;
} catch (e) {
console.log(e);
}
}
const res = await sendComment(COMMENT_SUBMIT_URL);
if (res.ok) {
getComments(props.posts_id);
}
}
return (
<>
<Grid
container
justify="space-evenly"
direction="row"
alignItems="center">
<Grid item xs={8}>
<TextField
id="comment"
fullWidth
multiline
rowsMax="10"
margin="normal"
variant="filled"
/>
</Grid>
<Grid item xs={3}>
<Button variant="contained" color="primary" onClick={handleSubmit}>
Submit
</Button>
</Grid>
</Grid>
<Grid container justify="space-left">
<Grid item justify="flex-start">
<Comments comments={comments} />
</Grid>
</Grid>
</>
);
}