在嵌套对象中，在React with Hooks中更新状态的正确方法是什么?
export Example = () => {
const [exampleState, setExampleState] = useState(
{masterField: {
fieldOne: "a",
fieldTwo: {
fieldTwoOne: "b"
fieldTwoTwo: "c"
}
}
})
如何使用setExampleState将exampleState更新为a(附加字段)?
const a = {
masterField: {
fieldOne: "a",
fieldTwo: {
fieldTwoOne: "b",
fieldTwoTwo: "c"
}
},
masterField2: {
fieldOne: "c",
fieldTwo: {
fieldTwoOne: "d",
fieldTwoTwo: "e"
}
},
}
}
b(改变值)?
const b = {masterField: {
fieldOne: "e",
fieldTwo: {
fieldTwoOne: "f"
fieldTwoTwo: "g"
}
}
})
我给您留下了一个实用函数来不可变地更新对象
/**
* Inmutable update object
* @param {Object} oldObject Object to update
* @param {Object} updatedValues Object with new values
* @return {Object} New Object with updated values
*/
export const updateObject = (oldObject, updatedValues) => {
return {
...oldObject,
...updatedValues
};
};
你可以这样用
const MyComponent = props => {
const [orderForm, setOrderForm] = useState({
specialities: {
elementType: "select",
elementConfig: {
options: [],
label: "Specialities"
},
touched: false
}
});
// I want to update the options list, to fill a select element
// ---------- Update with fetched elements ---------- //
const updateSpecialitiesData = data => {
// Inmutably update elementConfig object. i.e label field is not modified
const updatedOptions = updateObject(
orderForm[formElementKey]["elementConfig"],
{
options: data
}
);
// Inmutably update the relevant element.
const updatedFormElement = updateObject(orderForm[formElementKey], {
touched: true,
elementConfig: updatedOptions
});
// Inmutably update the relevant element in the state.
const orderFormUpdated = updateObject(orderForm, {
[formElementKey]: updatedFormElement
});
setOrderForm(orderFormUpdated);
};
useEffect(() => {
// some code to fetch data
updateSpecialitiesData.current("specialities",fetchedData);
}, [updateSpecialitiesData]);
// More component code
}
如果没有，您可以在这里找到更多实用程序:https://es.reactjs.org/docs/update.html
谢谢Philip，这帮助了我-我的用例是我有一个有很多输入字段的表单，所以我保持初始状态为对象，我不能更新对象状态。上面的帖子帮助了我:)
const [projectGroupDetails, setProjectGroupDetails] = useState({
"projectGroupId": "",
"projectGroup": "DDD",
"project-id": "",
"appd-ui": "",
"appd-node": ""
});
const inputGroupChangeHandler = (event) => {
setProjectGroupDetails((prevState) => ({
...prevState,
[event.target.id]: event.target.value
}));
}
<Input
id="projectGroupId"
labelText="Project Group Id"
value={projectGroupDetails.projectGroupId}
onChange={inputGroupChangeHandler}
/>
您必须使用Rest参数和扩展语法(https://javascript.info/rest-parameters-spread)，并设置一个以preState作为setState参数的函数。
不起作用(功能缺失)
[state, setState] = useState({})
const key = 'foo';
const value = 'bar';
setState({
...state,
[key]: value
});
确实工作!
[state, setState] = useState({})
const key = 'foo';
const value = 'bar';
setState(prevState => ({
...prevState,
[key]: value
}));
你想要创建状态的对象
let teams = {
team: [
{
name: "one",
id: "1"
},
]
}
使团队的状态为对象
const [state, setState] = useState(teams);
像这样更新状态
setState((prevState)=>({...prevState,team:[
...prevState.team,
{
name: "two",
id: "2"
}
]}))
更新后状态变为
{
team: [
{
name: "one",
id: "1"
},
{
name: "two",
id: "2"
}
]
}
要渲染项目根据当前状态使用地图功能
{state.team.map((curr_team) => {
return (
<div>
<p>{curr_team.id}</p>
<p>{curr_team.name}</p>
</div>
)
})}
