问题描述
您好,我有一个用于评分的预填充滑块,我用来自 API 的数据预填充它,如果用户滑动,我想更新 API 数据库。一切正常,除了滑块总是通过 useEffect 跳回到预填充的值。如何更改状态,以便用户的值优先于预填充的值?
这是我的代码:
const [ user ] = useContext(Context);
const location = useLocation();
const { pathname } = location;
const splitLocation = pathname.split("/");
const movieId = splitLocation[2];
const [ MovieResults,setMovieResults ] = useState([]);
const [ value,setValue ] = useState(5);
useEffect(() => {
let isMounted = true;
fetch(`${API_URL}account/xxxxxxxx/rated/movies?api_key=${API_KEY}&session_id=${user.sessionId}&sort_by=created_at.desc`)
.then(res => res.json())
.then(data => isMounted ? setMovieResults(data.results) : null)
.then(isMounted ? MovieResults.forEach((arrayItem) => {
if(arrayItem.id.toString() === movieId.toString()) {
setValue(arrayItem.rating);
}
}) : null)
return () => { isMounted = false };
},[user.sessionId,MovieResults,movieId]);
const changeSlider = (e) => {
// This value should override the default value from the api
setValue(e.currentTarget.value);
};
return (
<div>
<input
type="range"
min="1"
max="10"
className="rate-slider"
value={value}
onChange={e => changeSlider(e)}
/>
{value}
<p>
<button className="rate-button" onClick={() => callback(value)}>Rate</button>
</p>
</div>
)
感谢帮助。
解决方法
按照您的一般方法,这对我来说似乎很好:
const fetch = () => new Promise(resolve => setTimeout(() =>
resolve({json: () => ({rating: 4})}),1000));
const App = () => {
const [sliderVal,setSliderVal] = React.useState(0);
const [loading,setLoading] = React.useState(true);
React.useEffect(() => {
fetch("foo")
.then(res => res.json())
.then(data => {
setLoading(false);
setSliderVal(data.rating);
});
},[]);
const handleSliderChange = evt => {
setSliderVal(evt.target.value);
};
return (
<div>
{loading
? <p>loading...</p>
: <div>
<input
type="range"
min="1"
max="10"
value={sliderVal}
onChange={handleSliderChange}
/>
{sliderVal}
</div>
}
</div>
);
};
ReactDOM.render(<App />,document.body);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.1/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.1/umd/react-dom.production.min.js"></script>
我终于设法解决了它。我需要根据用户滑动滑块的条件将两个 setValue 中的一个优先于另一个。到现在我都不知道useRef,有了这个钩子我可以管理它。代码如下:
const [ user ] = useContext(Context);
const location = useLocation();
const { pathname } = location;
const splitLocation = pathname.split("/");
const movieId = splitLocation[2];
const [ MovieResults,setMovieResults ] = useState([]);
const [ value,setValue ] = useState(5);
const ref = useRef(0);
useEffect(() => {
let isMounted = true;
fetch(`${API_URL}account/jensgeffken/rated/movies?api_key=${API_KEY}&session_id=${user.sessionId}&sort_by=created_at.desc`)
.then(res => res.json())
.then(data => isMounted ? setMovieResults(data.results) : null)
.then(isMounted ? MovieResults.forEach((arrayItem) => {
if(arrayItem.id.toString() === movieId.toString()) {
//console.log(ref.current)
if(ref.current === 0) {
setValue(arrayItem.rating);
}
}
}) : null)
return () => { isMounted = false };
},[user.sessionId,MovieResults,movieId]);
const handleSlide = (e) => {
ref.current = e.currentTarget.value
setValue(ref.current);
}
return (
<div>
<input
type="range"
min="1"
max="10"
className="rate-slider"
value={value}
onChange={e => handleSlide(e)}
/>
{value}
<p>
<button className="rate-button" onClick={() => callback(value)}>Rate</button>
</p>
</div>
)