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"
}
}
})
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
}));
function App() {
const [todos, setTodos] = useState([
{ id: 1, title: "Selectus aut autem", completed: false },
{ id: 2, title: "Luis ut nam facilis et officia qui", completed: false },
{ id: 3, title: "Fugiat veniam minus", completed: false },
{ id: 4, title: "Aet porro tempora", completed: true },
{ id: 5, title: "Laboriosam mollitia et enim quasi", completed: false }
]);
const changeInput = (e) => {todos.map(items => items.id === parseInt(e.target.value) && (items.completed = e.target.checked));
setTodos([...todos], todos);}
return (
<div className="container">
{todos.map(items => {
return (
<div key={items.id}>
<label>
<input type="checkbox"
onChange={changeInput}
value={items.id}
checked={items.completed} /> {items.title}</label>
</div>
)
})}
</div>
);
}