我在子组件中有一组按钮,在单击时将相应的状态值设置为true或false。我在这个子组件中也有一个useEffect钩子,它也依赖于所有这些状态值,因此,如果单击按钮,则此钩子会调用setFilter,它作为道具从父级传递下来。
const Filter = ({ setFilter }) => {
const [cycling, setCycling] = useState(true);
const [diy, setDiy] = useState(true);
useEffect(() => {
setFilter({
cycling: cycling,
diy: diy
});
}, [cycling, diy]);
return (
<Fragment>
<Row>
<Col>
<Button block onClick={() => setCycling(!cycling)}>cycling</Button>
</Col>
<Col>
<Button block onClick={() => setdIY(!DIY)}>DIY</Button>
</Col>
</Row>
</Fragment>
);
};
在父组件中,我显示项目列表。我在父级中有两种效果,一种是初始加载项目,另一种是在更改过滤器时触发。为了简洁起见,我删除了大多数代码,但是我认为我的使用归结为这样一个事实,即在渲染ItemDashboard时,过滤器被调用了两次。我该如何阻止这种情况的发生,或者我应该以其他方式看待这种情况。
const ItemDashboard = () => {
const [filter, setFilter] = useState(null);
useEffect(() => {
console.log('on mount');
}, []);
useEffect(() => {
console.log('filter');
}, [filter]);
return (
<Container>..
<Filter setFilter={setFilter} />
</Container>
);
}
答案 0 :(得分:1)
是的,您可以在子组件中useEffect
,具体取决于状态,这也是您通常如何实现受控制和不受控制的组件:
const NOOP = () => {};
// Filter
const Child = ({ onChange = NOOP }) => {
const [counter, setCounter] = useState(0);
useEffect(() => {
onChange(counter);
}, [counter, onChange]);
const onClick = () => setCounter(c => c + 1);
return (
<div>
<div>{counter}</div>
<button onClick={onClick}>Increase</button>
</div>
);
};
// ItemDashboard
const Parent = () => {
const [value, setState] = useState(null);
useEffect(() => {
console.log(value);
}, [value]);
return <Child onChange={setState} />;
};
答案 1 :(得分:1)
我猜,您正在寻找lift state up成为普通父母的方式。
为此,您可以将子组件的事件处理程序(作为道具传递)绑定到其公共父项中的所需回调。
以下现场演示演示了该概念:
const { render } = ReactDOM,
{ useState } = React
const hobbies = ['cycling', 'DIY', 'hiking']
const ChildList = ({list}) => (
<ul>
{list.map((li,key) => <li {...{key}}>{li}</li>)}
</ul>
)
const ChildFilter = ({onFilter, visibleLabels}) => (
<div>
{
hobbies.map((hobby,key) => (
<label {...{key}}>{hobby}
<input
type="checkbox"
value={hobby}
checked={visibleLabels.includes(hobby)}
onChange={({target:{value,checked}}) => onFilter(value, checked)}
/>
</label>))
}
</div>
)
const Parent = () => {
const [visibleHobbies, setVisibleHobbies] = useState(hobbies),
onChangeVisibility = (hobby,visible) => {
!visible ?
setVisibleHobbies(visibleHobbies.filter(h => h != hobby)) :
setVisibleHobbies([...visibleHobbies, hobby])
}
return (
<div>
<ChildList list={visibleHobbies} />
<ChildFilter onFilter={onChangeVisibility} visibleLabels={visibleHobbies} />
</div>
)
}
render (
<Parent />,
document.getElementById('root')
)
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.12.0/umd/react.production.min.js"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.11.0/umd/react-dom.production.min.js"></script><div id="root"></div>