[英]React children component not re-rendering after parent state changes
我是 React 新手,正在尝试创建一个简单的纸牌游戏。 当一张卡片被点击时,它应该被选中并分配一个类名“selectedCard”。 因此,当它重新渲染时,选定的卡片将被抬起。 但是,选择的卡并没有抬起 onClick,我的猜测是它没有重新渲染。
这是我的代码片段:
播放器.js:
const Player = (props) =>{
const [selectedCards, setSelectCard] = useState([]);
const selectCard = (card) => {
let newSelectedCards = selectedCards
if(newSelectedCards.includes(card) ) {
newSelectedCards.splice(newSelectedCards.indexOf(card), 1)
} else {
newSelectedCards.push(card)
}
setSelectCard(newSelectedCards)
console.log('changed');
}
return(
<div className="player-container">
{props.cards && props.cards.map((card, i) => {
let selected = selectedCards.includes(card)
return(<Card key={i} card={card} user="player" selectCard={selectCard} selected={selected}/>)
}
)}
)
}
Card.js
const Card = (props) =>{
const path = props.card.imagePath
const [selected, setSelected] = useState(props.selected)
useEffect(() => { setSelected(props.selected) }, [props.selected]);
{/*My effort to make it work*/}
const classname = (selected) ? "selectedcard" : ""
return(
<img onClick={() => props.selectCard(props.card)} className={"card " + classname} alt = "card-image" src={images[path]}/>)
}
css
.selectedcard{
margin-bottom: 40px;
border-radius: 6px;
box-shadow: 0px 0px 5px #fff !important;
}
您不应该在更新 state 时对其进行突变,如果您这样做,React 会在参考检查中看到您的参考是相同的,并假设没有任何变化并且不会触发重新渲染。
在更新 react state 时遵循不变性的概念。 您可以使用Array.prototype.slice
更新它,并使用spread syntax
删除项目并使用Array.prototype.concat
添加项目
const selectCard = (card) => {
let newSelectedCards =[];
if(newSelectedCards.includes(card) ) {
const index = selectedCards.indexOf(card)
newSelectedCards = [...selectedCards.slice(0, index), ...selectedCards.slice(index + 1)]
} else {
newSelectedCards = selectedCards.concat([card]);
}
setSelectCard(newSelectedCards)
console.log('changed');
}
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