[英]React children component not re-rendering after parent state changes
我是 React 新手,正在嘗試創建一個簡單的紙牌游戲。 當一張卡片被點擊時,它應該被選中並分配一個類名“selectedCard”。 因此,當它重新渲染時,選定的卡片將被抬起。 但是,選擇的卡並沒有抬起 onClick,我的猜測是它沒有重新渲染。
這是我的代碼片段:
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;
}
您不應該在更新 state 時對其進行突變,如果您這樣做,React 會在參考檢查中看到您的參考是相同的,並假設沒有任何變化並且不會觸發重新渲染。
在更新 react state 時遵循不變性的概念。 您可以使用Array.prototype.slice
更新它,並使用spread syntax
刪除項目並使用Array.prototype.concat
添加項目
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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