当我有多个子组件时，如何将值从子组件传递给父组件

Question

我创建了多个组件，它们具有相同的层次结构，在它们内部我还调用其他组件调用，现在我想在我的上创建函数，这些函数将更新我作为道具传递给我的组件的值。我设法将函数作为道具传递，但无法将子项的值作为参数传递给函数，因此我只能更新特定于该子项的道具。

应用

function App() {
// eslint-disable-next-line
const [content, setContent] = useState(images)
const [count, setCount] = useState(content.votes)
console.log(count)
const upVote = (id) => {
alert('up =>', id)
}
const downVote = () => {
alert('down')
}
return (
<div className="App">
<div className="grid">
{content.map((picture, index) => {
return <Card key={index} picture={picture} teste={[upVote, downVote]}/>
})
}
</div>
</div>
)
}

卡片

function Card({ picture, teste }) {
return (
<div className="card">
<div className="container">
<img
width="300"
alt={`id: ${picture.id}`}
src={picture.src}
className="image"
/>
<Options votes={0} originalPost={picture.original_post} teste={teste[0]}/>
</div>
</div>
)
}

选项

function Options({ votes, originalPost, teste }) {
const [count, setCount] = useState(votes)
const [styling, setStyling] = useState('#696969')
function countStyle(count) {
if (count > 0){
setStyling('#008000')
} else if (count < 0) {
setStyling('#B22222')
} else {
setStyling('#696969')
}
}
return (
<div>
<button onClick={() => teste(count)} className="buttons">teste</button>        
<button title="Down vote" onClick={() => { 
setCount(count - 1)
countStyle(count-1)
// style(count - 1)
}} className="buttons">-</button>
<span title="Vote counter" style={{color: styling}} className="counter">{count}</span>
<button title="Up vote" onClick={() => {
setCount(count + 1)
// style(count + 1)
countStyle(count +1)
}} className="buttons">+</button><br></br>
<a href={originalPost} 
target="_blank"
title="Click to check the original post"
rel="noopener noreferrer"
className="link">Original post</a>
</div>
)
}

Answer 1

我首先将您的状态合并到应用程序组件中。在每个图片对象的内容数组中保存投票。将向上投票和向下投票功能传递给每个孩子，并通过点击按钮呼叫他们。我也会根据道具来计算造型，而不是使用状态。

应用

function App() {
let initialstate = images.map(image => {
image.votes = 0;
return image;
});
const [content, setContent] = useState(initialstate);
const upVote = index => {
setContent(content[index].votes + 1);
};
const downVote = index => {
setContent(content[index].votes - 1);
};
return (
<div className="App">
<div className="grid">
{content.map((picture, index) => {
return <Card key={index} picture={picture} index={index} upVote={upVote} downVote={downVote} />;
})}
</div>
</div>
);
}

卡片

function Card({ index, picture, ...props }) {
const upVote = () => props.upVote(index);
const downVote = () => props.downVote(index);
return (
<div className="card">
<div className="container">
<img
width="300"
alt={`id: ${picture.id}`}
src={picture.src}
className="image"
/>
<Options votes={picture.votes} originalPost={picture.original_post} upVote={upVote} downVote={downVote}/>
</div>
</div>
)

选项

function Options({ votes, originalPost, upVote, downVote }) {
let styling = '#696969';
if (count > 0) {
styling = '#008000';
} else if (count < 0) {
styling = '#B22222';
} else {
styling = '#696969';
}
return (
<div>
<button title="Down vote" onClick={downVote} className="buttons">
-
</button>
<span title="Vote counter" style={{ color: styling }} className="counter">
{votes}
</span>
<button title="Up vote" onClick={upVote} className="buttons">
+
</button>
<br></br>
<a
href={originalPost}
target="_blank"
title="Click to check the original post"
rel="noopener noreferrer"
className="link"
>
Original post
</a>
</div>
);
}