如何使用自定义钩子中的数据在 useState 中初始化状态?

Question

我正在学习 React Hooks。 而且我正在努力初始化使用自定义钩子从服务器获取的数据。

我想我用错了钩子。 我的代码如下。

const useFetchLocation = () => {
const [currentLocation, setCurrentLocation] = useState([]);
const getCurrentLocation = (ignore) => {
...
};
useEffect(() => {
let ignore = false;
getCurrentLocation(ignore);
return () => { ignore = true; }
}, []);
return {currentLocation};
};
const useFetch = (coords) => {
console.log(coords);
const [stores, setStores] = useState([]);
const fetchData = (coords, ignore) => {
axios.get(`${URL}`)
.then(res => {
if (!ignore) {
setStores(res.data.results);
}
})
.catch(e => {
console.log(e);
});
};
useEffect(() => {
let ignore = false;
fetchData(ignore);
return () => {
ignore = true;
};
}, [coords]);
return {stores};
}
const App = () => {
const {currentLocation} = useFetchLocation();
const {stores} = useFetch(currentLocation); // it doesn't know what currentLocation is.
...

显然，它不能同步工作。 但是，我相信有正确的方法可以做到这一点。 在这种情况下，我该怎么办？ 如果您给我任何想法，我将不胜感激。 谢谢。

Answer 1

不确定所有ignore变量是关于什么的，但是如果设置了coords，您可以检查效果。只有当设置coords时，您才应该发出 axios 请求。

const useFetchLocation = () => {
// Start out with null instead of an empty array, this makes is easier to check later on
const [currentLocation, setCurrentLocation] = useState(null);
const getCurrentLocation = () => {
// Somehow figure out the current location and store it in the state
setTimeout(() => {
setCurrentLocation({ lat: 1, lng: 2 });
}, 500);
};
useEffect(() => {
getCurrentLocation();
}, []);
return { currentLocation };
};
const useFetch = coords => {
const [stores, setStores] = useState([]);
const fetchData = coords => {
console.log("make some HTTP request using coords:", coords);
setTimeout(() => {
console.log("pretending to receive data");
setStores([{ id: 1, name: "Store 1" }]);
}, 500);
};
useEffect(() => {
/*
* When the location is set from useFetchLocation the useFetch code is
* also triggered again. The first time coords is null so the fetchData code
* will not be executed. Then, when the coords is set to an actual object
* containing coordinates, the fetchData code will execute.
*/
if (coords) {
fetchData(coords);
}
}, [coords]);
return { stores };
};
function App() {
const { currentLocation } = useFetchLocation();
const { stores } = useFetch(currentLocation);
return (
<div className="App">
<ul>
{stores.map(store => (
<li key={store.id}>{store.name}</li>
))}
</ul>
</div>
);
}

工作沙盒(没有注释(https://codesandbox.io/embed/eager-elion-0ki0v