这不是一个特定的错误，我在调用函数时遇到了一个无限的 post 循环
getLikes = (id) => {
// console.log(id);
this.props.getLikeCount(id)
console.log(this.props.likeCount)
}
视觉上看起来像这样
这是一个无限循环。我们重构了代码，以便用户可以为帖子添加赞、检索特定帖子的赞数量以及更新赞的状态。
Like.js
import React, { Component } from 'react';
import ReactDOM from 'react-dom'
import { FontAwesomeIcon } from '@fortawesome/react-fontawesome';
import { faCoffee, faAdjust } from '@fortawesome/free-solid-svg-icons';
import {connect} from 'react-redux';
import { getLikeCount} from '../actions/';
class Like extends Component{
constructor(props){
super(props);
this.state = {
likes: null
}
}
getLikes = (id) => {
// console.log(id);
this.props.getLikeCount(id)
console.log(this.props.likeCount)
}
render(){
return(
<div style={{float:'right', fontSize: '1.5em', color:'tomato'}} >
<i style={{ marginRight: '140px'}} className="fa fa-heart-o">
<span style={{ marginLeft: '6px'}}>
<a href="#" onClick={this.props.like}>Like </a>
{this.getLikes(this.props.postId)}
</span>
{/* gets the like counts */}
{this.props.likeCount}
</i>
</div>
)
}
}
const mapStateToProps = (state) => ({
isEditingId: state.post.isEditingId,
likeCount:state.post.likes
})
const mapDispatchToProps = (dispatch) => ({
getLikeCount: (id) => dispatch(getLikeCount(id)),
// Pass id to the DeletePost functions.
});
export default connect(mapStateToProps, mapDispatchToProps)(Like);
Actions.js
export const postLike = (id) => {
return (dispatch) => {
// console.log(userId);
return Axios.post('/api/posts/like', {
postId: id
}).then( (like) => {
dispatch({type: ADD_LIKE})
// console.log('you have liked this', like)
}).catch( (err)=> {
console.log('there seem to be an error', err);
})
}
}
export const getLikeCount = (id) => {
return (dispatch, getState) => {
return Axios.get(`/api/posts/likes/count/${id}`)
.then( (res) => {
const data = res.data
console.log(data); // logs data and i can see an array
dispatch({type: GET_LIKES_COUNT, data})
})
}
}
reducer
import { ADD_LIKE, GET_LIKES_COUNT} from '../actions/';
const initialState = {
likes:0,
}
export default (state = initialState, action) => {
switch (action.type) {
case GET_LIKES_COUNT:
// console.log(action.data)
return({
...state,
likes:action.data
})
case ADD_LIKE:
return({
...state,
likes: state.likes + 1
})
default:
return state
}
}
PostList.js
import React, { Component } from 'react';
import Paper from '@material-ui/core/Paper';
import Button from '@material-ui/core/Button';
import Typography from '@material-ui/core/Typography';
import moment from 'moment';
import {connect} from 'react-redux';
import {DeletePost, getLikeCount, postLike, UpdatePost,EditChange, DisableButton} from '../actions/';
import PostItem from './PostItem';
const Styles = {
myPaper: {
margin: '20px 0px',
padding: '20px'
}
}
class PostList extends Component{
constructor(props){
super(props);
this.state ={
title: '',
}
}
// Return a new function. Otherwise the DeletePost action will be dispatch each
// time the Component rerenders.
removePost = (id) => () => {
this.props.DeletePost(id);
}
onChange = (e) => {
e.preventDefault();
this.setState({
title: e.target.value
})
}
clickLike = (id) => {
this.props.postLike(id);
}
formEditing = (id) => ()=> {;
this.props.EditChange(id);
}
render(){
const {posts} = this.props;
return (
<div>
{posts.map((post, i) => (
<Paper key={post.id} style={Styles.myPaper}>
{/* {...post} prevents us from writing all of the properties out */}
<PostItem
clickLike={this.clickLike(post.id)}
myTitle={this.state.title}
editChange={this.onChange}
editForm={this.formEditing}
isEditing={this.props.isEditingId === post.id}
removePost={this.removePost}
{...post}
/>
</Paper>
))}
</div>
)
}
}
const mapStateToProps = (state) => ({
isEditingId: state.post.isEditingId,
})
const mapDispatchToProps = (dispatch) => ({
// pass creds which can be called anything, but i just call it credentials but it should be called something more
// specific.
EditChange: (id) => dispatch(EditChange(id)),
UpdatePost: (creds) => dispatch(UpdatePost(creds)),
getLikeCount: (id) => dispatch(getLikeCount(id)),
postLike: (id) => dispatch( postLike(id)),
// Pass id to the DeletePost functions.
DeletePost: (id) => dispatch(DeletePost(id))
});
export default connect(mapStateToProps, mapDispatchToProps)(PostList);
PostItem.js
import React, { Component } from 'react';
import Paper from '@material-ui/core/Paper';
import Button from '@material-ui/core/Button';
import Typography from '@material-ui/core/Typography';
import moment from 'moment';
import Editable from './Editable';
import {connect} from 'react-redux';
import {UpdatePost, getLikeCount, postLike} from '../actions/';
import Like from './Like';
import Axios from '../Axios';
const Styles = {
myPaper: {
margin: '20px 0px',
padding: '20px'
},
button:{
marginRight:'30px'
}
}
class PostItem extends Component{
constructor(props){
super(props);
this.state = {
disabled: false,
}
}
onUpdate = (id, title) => () => {
// we need the id so express knows what post to update, and the title being that only editing the title.
if(this.props.myTitle !== null){
const creds = {
id, title
}
this.props.UpdatePost(creds);
}
}
render(){
const {title, id, userId, removePost, createdAt, post_content, username, editForm, isEditing, editChange, myTitle, postUpdate, likes, clickLike} = this.props
return(
<div>
<Typography variant="h6" component="h3">
{/* if else teneray operator */}
{isEditing ? (
<Editable editField={myTitle ? myTitle : title} editChange={editChange}/>
): (
<div>
{title}
</div>
)}
</Typography>
<Typography component="p">
{post_content}
<h5>
by: {username}</h5>
<Typography color="textSecondary">{moment(createdAt).calendar()}</Typography>
<Like like={clickLike} postId={id}/>
</Typography>
{!isEditing ? (
<Button variant="outlined" type="submit" onClick={editForm(id)}>
Edit
</Button>
):(
// pass id, and myTitle which as we remember myTitle is the new value when updating the title
<div>
<Button
disabled={myTitle.length <= 3}
variant="outlined"
onClick={this.onUpdate(id, myTitle)}>
Update
</Button>
<Button
variant="outlined"
style={{marginLeft: '0.7%'}}
onClick={editForm(null)}>
Close
</Button>
</div>
)}
{!isEditing && (
<Button
style={{marginLeft: '0.7%'}}
variant="outlined"
color="primary"
type="submit"
onClick={removePost(id)}>
Remove
</Button>
)}
</div>
)
}
}
const mapStateToProps = (state) => ({
isEditingId: state.post.isEditingId,
})
const mapDispatchToProps = (dispatch) => ({
// pass creds which can be called anything, but i just call it credentials but it should be called something more
// specific.
UpdatePost: (creds) => dispatch(UpdatePost(creds)),
getLikeCount: (id) => dispatch(getLikeCount(id)),
postLike: (id) => dispatch( postLike(id))
// Pass id to the DeletePost functions.
});
export default connect(null, mapDispatchToProps)(PostItem);
Posts.js
import React, { Component } from 'react';
import PostList from './PostList';
import {connect} from 'react-redux';
import { withRouter, Redirect} from 'react-router-dom';
import {GetPosts} from '../actions/';
const Styles = {
myPaper:{
margin: '20px 0px',
padding:'20px'
}
,
wrapper:{
padding:'0px 60px'
}
}
class Posts extends Component {
state = {
posts: [],
loading: true,
isEditing: false,
}
async componentWillMount(){
await this.props.GetPosts();
this.setState({ loading: false })
const reduxPosts = this.props.myPosts;
const ourPosts = reduxPosts
console.log(reduxPosts); // shows posts line 35
}
render() {
const {loading} = this.state;
const { myPosts} = this.props
if (!this.props.isAuthenticated) {
return (<Redirect to='/signIn' />);
}
if(loading){
return "loading..."
}
return (
<div className="App" style={Styles.wrapper}>
<h1> Posts </h1>
<PostList posts={myPosts}/>
</div>
);
}
}
const mapStateToProps = (state) => ({
isAuthenticated: state.user.isAuthenticated,
myPosts: state.post.posts
})
const mapDispatchToProps = (dispatch, state) => ({
GetPosts: () => dispatch( GetPosts())
});
export default withRouter(connect(mapStateToProps,mapDispatchToProps)(Posts));
API 调用 sequelize express 后端
router.get('/likes/count/:postId', (req, res) => {
models.Likes.count ({
where: { postId: req.params.postId }
})
.then (likes=> res.status(200).json(likes))
.catch (e => res.status(404))
});
最佳答案
考虑一种情况，您的数据如下所示:
posts=[
{id: 0, msg: foo, likes: 0},
{id: 1, msg: bar, likes: 1}
]
并且您想为其中一个帖子发送一个赞，例如带有 id:0 的帖子
在您的文件组件中:
import React, {Component} from 'react';
import {connect} from "react-redux";
import {upVote} from "./action";
class MyApp extends Component {
handleUpVote = (id) => this.props.dispatch(upVote(id));
render() {
return (
<div>
{this.props.posts.map(post => (
<div key={post.id}>
<button onClick={() => this.handleUpVote(post.id)}>Like</button>
<p>{post.likes}</p>
</div>
))}
</div>
);
}
}
const mapStateToProps = state => {
const posts = state.posts;
return {posts}
};
export default connect(mapStateToProps)(MyApp);
在 action.js 中:
const UP_VOTE_LIKES = 'UP_VOTE_LIKES';
const upVote = (id) => ({type: UP_VOTE_LIKES, id});
export {
UP_VOTE_LIKES,
upVote,
}
最后，在您的 reducer 中:
import {UP_VOTE_LIKES} from "./action";
const initialState = {
posts: []
};
const reducer = (state = initialState, action) => {
switch (action.type) {
case(UP_VOTE_LIKES):
return {
...state,
posts: state.posts.map(post => {
if (post.id === action.id) {
return {
...post,
likes: post.likes + 1
}
} else return post
})
};
default:
return state
}
};
export default reducer
首先，看reducer很复杂，但实际上并不奇怪。
关于reactjs - 调用 Action 时的无限后期循环，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55786557/