Reactjs 将React类组件转换为React钩子
嗨,我是新来的反应者,我正在做一个模因发生器。我试图将它从一个类转换为react钩子,但不确定为什么它不工作。这就是我到目前为止所做的,当我尝试生成一个新图像时,我得到了一个错误Reactjs 将React类组件转换为React钩子,reactjs,react-native,Reactjs,React Native,嗨,我是新来的反应者,我正在做一个模因发生器。我试图将它从一个类转换为react钩子,但不确定为什么它不工作。这就是我到目前为止所做的,当我尝试生成一个新图像时,我得到了一个错误 import React, { useEffect, useState } from "react" function MemeGenerator() { const [newText, setNewText] = useState({ topText: "",
import React, { useEffect, useState } from "react"
function MemeGenerator() {
const [newText, setNewText] = useState({
topText: "",
lastName: ""
})
const [randomImg, setrandomImg] = useState("http://i.imgflip.com/1bij.jpg")
const [allMemeImgs, setallMemeImages] = useState([])
useEffect(()=> {
fetch("https://api.imgflip.com/get_memes")
.then(response => response.json())
.then(response => {
const {memes} = response.data
setallMemeImages({allMemeImgs: memes})
})
},[])
function handleChange(event) {
const {name, value} = event.target
setNewText({
...newText,
[name]: value
})
}
// error is on this function I believe
function handleSubmit(event) {
event.preventDefault()
const randNum = Math.floor(Math.random() * allMemeImgs.length)
alert(randNum)
const randMemeImg = allMemeImgs[randNum].url
setrandomImg(randMemeImg)
}
return (
<div>
<form className="meme-form" onSubmit={handleSubmit}>
<input
type="text"
name="topText"
placeholder="Top Text"
value={newText.topText}
onChange={handleChange}
/>
<input
type="text"
name="bottomText"
placeholder="Bottom Text"
value={newText.bottomText}
onChange={handleChange}
/>
<button>Gen</button>
</form>
<div className="meme">
<img src={randomImg} alt="" />
<h2 className="top">{newText.topText}</h2>
<h2 className="bottom">{newText.bottomText}</h2>
</div>
</div>
)
}
import React,{useffect,useState}来自“React”
函数MemeGenerator(){
常量[newText,setNewText]=useState({
topText:“”,
姓氏:“
})
常量[randomImg,setrandomImg]=useState(“http://i.imgflip.com/1bij.jpg")
const[allMemeImgs,setallMemeImages]=useState([]
useffect(()=>{
取回(“https://api.imgflip.com/get_memes")
.then(response=>response.json())
。然后(响应=>{
const{memes}=response.data
setallMemeImages({allMemeImgs:memes})
})
},[])
函数句柄更改(事件){
常量{name,value}=event.target
设置新文本({
…新文本,
[名称]:值
})
}
//我相信这个函数有错误
函数handleSubmit(事件){
event.preventDefault()
const randNum=Math.floor(Math.random()*allMemeImgs.length)
警报(随机数)
const randMemeImg=allMemeImgs[randNum].url
setrandomImg(randMemeImg)
}
返回(
消息
{newText.topText}
{newText.bottomText}
)
}
我以前工作过的是:
import React, {Component} from "react"
class MemeGenerator extends Component {
constructor() {
super()
this.state = {
topText: "",
bottomText: "",
randomImg: "http://i.imgflip.com/1bij.jpg",
allMemeImgs: []
}
this.handleChange = this.handleChange.bind(this)
this.handleSubmit = this.handleSubmit.bind(this)
}
componentDidMount() {
fetch("https://api.imgflip.com/get_memes")
.then(response => response.json())
.then(response => {
const {memes} = response.data
this.setState({ allMemeImgs: memes })
})
}
handleChange(event) {
const {name, value} = event.target
this.setState({ [name]: value })
}
handleSubmit(event) {
event.preventDefault()
const randNum = Math.floor(Math.random() * this.state.allMemeImgs.length)
const randMemeImg = this.state.allMemeImgs[randNum].url
this.setState({ randomImg: randMemeImg })
}
render() {
return (
<div>
<form className="meme-form" onSubmit={this.handleSubmit}>
<input
type="text"
name="topText"
placeholder="Top Text"
value={this.state.topText}
onChange={this.handleChange}
/>
<input
type="text"
name="bottomText"
placeholder="Bottom Text"
value={this.state.bottomText}
onChange={this.handleChange}
/>
<button>Gen</button>
</form>
<div className="meme">
<img src={this.state.randomImg} alt="" />
<h2 className="top">{this.state.topText}</h2>
<h2 className="bottom">{this.state.bottomText}</h2>
</div>
</div>
)
}
import React,{Component}来自“React”
类MemeGenerator扩展组件{
构造函数(){
超级()
此.state={
topText:“”,
底部文本:“”,
随机数:http://i.imgflip.com/1bij.jpg",
所有成员:[]
}
this.handleChange=this.handleChange.bind(this)
this.handleSubmit=this.handleSubmit.bind(this)
}
componentDidMount(){
取回(“https://api.imgflip.com/get_memes")
.then(response=>response.json())
。然后(响应=>{
const{memes}=response.data
this.setState({allMemeImgs:memes})
})
}
手变(活动){
常量{name,value}=event.target
this.setState({[name]:value})
}
handleSubmit(事件){
event.preventDefault()
const randNum=Math.floor(Math.random()*this.state.allMemeImgs.length)
const randMemeImg=this.state.allMemeImgs[randNum].url
this.setState({randomImg:randMemeImg})
}
render(){
返回(
消息
{this.state.topText}
{this.state.bottomText}
)
}
错误显示:
TypeError:undefined不是对象(计算'allMemeImgs[randNum].url')您希望为allMemeImgs状态初始化数组
const [allMemeImgs, setallMemeImages] = useState([])
但已将其配置为此特定useffecthook中的对象
useEffect(()=> {
fetch("https://api.imgflip.com/get_memes")
.then(response => response.json())
.then(response => {
const {memes} = response.data
setallMemeImages({allMemeImgs: memes}) // culprit here
})
},[])
在线发布:
setallMemeImages({allMemeImgs: memes})
建议将此行更改为:
setallMemeImages([...memes]);
allMemeImgs
是本地状态的数组。但是这里setallMemeImages({allMemeImgs:memes})
将其设置为对象
将其更改为
setallMemeImages((prev)=>[…prev,memes])
注意您也可以使用setallMemeImages([…memes]);
但是如果出现类型错误,请使用setallMemeImages(memes);
,如果您得到randMemeImg
的类型从不出错,请使用:
const randMemeImg = allMemeImgs[randNum];
setrandomImg(Object(randMemeImg).url);
函数MemeGenerator(){
常量[newText,setNewText]=React.useState({
topText:“”,
正文:“”
})
常量[randomImg,setrandomImg]=React.useState(“http://i.imgflip.com/1bij.jpg")
const[allMemeImgs,setallMemeImages]=React.useState([]
React.useffect(()=>{
取回(“https://api.imgflip.com/get_memes")
.then(response=>response.json())
。然后(响应=>{
const{memes}=response.data
setallMemeImages([…memes]);
})
},[])
函数句柄更改(事件){
常量{name,value}=event.target
设置新文本({
…新文本,
[名称]:值
})
}
函数handleSubmit(事件){
event.preventDefault()
const randNum=Math.floor(Math.random()*allMemeImgs.length)
警报(随机数)
const randMemeImg=allMemeImgs[randNum].url
setrandomImg(randMemeImg)
}
返回(
消息
{newText.topText}
{newText.bottomText}
)
}
ReactDOM.render(,document.querySelector(“#app”);
setallMemeImages({allMemeImgs:memes})
应该是setallMemeImages(memes)
它应该是setallMemeImages(memes);
const randMemeImg = allMemeImgs[randNum];
setrandomImg(Object(randMemeImg).url);