Javascript 如何在 React Hooks 中的对象数组中更新状态 onchange
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How do I update states onchange in an array of object in React Hooks
提问by reddy
I have retrieved datas stored using useState in an array of object, the datas was then outputted into form fields. And now I want to be able to update the fields (state) as I type.
我已经检索了使用 useState 存储在对象数组中的数据，然后将数据输出到表单字段中。现在我希望能够在我输入时更新字段（状态）。
I have seem examples on people updating the state for property in array, but never for state in an array of object, so I don't know how to do it. I've got the index of the object passed to the callback function but I didn't know how to update the state using it.
我似乎有关于人们更新数组中属性状态的示例，但从未更新过对象数组中的状态，所以我不知道该怎么做。我已经将对象的索引传递给回调函数，但我不知道如何使用它更新状态。
// sample datas structure
const datas = [
{
id: 1,
name: 'john',
gender: 'm'
}
{
id: 2,
name: 'mary',
gender: 'f'
}
]
const [datas, setDatas] = useState([]);
const updateFieldChanged = index => e => {
console.log('index: ' + index);
console.log('property name: '+ e.target.name);
setData() // ??
}
return (
<React.Fragment>
{ datas.map( (data, index) => {
<li key={data.name}>
<input type="text" name="name" value={data.name} onChange={updateFieldChanged(index)} />
</li>
})
}
</React.Fragment>
)
回答by Maria Miller
Here is how you do it:
这是你如何做到的：
// sample datas structure
/* const datas = [
{
id: 1,
name: 'john',
gender: 'm'
}
{
id: 2,
name: 'mary',
gender: 'f'
}
] */ // make sure to set the default value in the useState call (I already fixed it)
const [datas, setDatas] = useState([
{
id: 1,
name: 'john',
gender: 'm'
}
{
id: 2,
name: 'mary',
gender: 'f'
}
]);
const updateFieldChanged = index => e => {
console.log('index: ' + index);
console.log('property name: '+ e.target.name);
let newArr = [...datas]; // copying the old datas array
newArr[index] = e.target.value; // replace e.target.value with whatever you want to change it to
setDatas(newArr); // ??
}
return (
<React.Fragment>
{ datas.map( (data, index) => {
<li key={data.name}>
<input type="text" name="name" value={data.name} onChange={updateFieldChanged(index)} />
</li>
})
}
</React.Fragment>
)
回答by spender
You can do this without mutation by mapping your old array into a new one, swapping what you want to change for an updated item along the way.
您可以通过将旧数组映射到新数组，并在此过程中将要更改的内容交换为更新的项目，而无需更改即可完成此操作。
setDatas(datas.map(item => item.id === index ? {...item, someProp : "changed"} : item ))
