我建议在这里看看Dan Abramov(React核心维护者之一)的答案:
我认为您正在使它变得比所需的更加复杂。
function Example() {
const [data, dataSet] = useState<any>(null)
useEffect(() => {
async function fetchMyAPI() {
let response = await fetch('api/data')
response = await response.json()
dataSet(response)
}
fetchMyAPI()
}, [])
return <div>{JSON.stringify(data)}</div>
}
从长远来看,我们会阻止这种模式,因为它会鼓励比赛条件。例如-在通话开始和结束之间可能会发生任何事情,并且您可能会获得新的道具。相反,我们建议使用Suspense进行数据提取,看起来更像
const response = MyAPIResource.read();
而且没有效果。但是与此同时,您可以将异步内容移到一个单独的函数中并进行调用。
您可以在此处阅读更多有关实验性悬念的信息。
如果要在eslint之外使用函数。
function OutsideUsageExample() {
const [data, dataSet] = useState<any>(null)
const fetchMyAPI = useCallback(async () => {
let response = await fetch('api/data')
response = await response.json()
dataSet(response)
}, [])
useEffect(() => {
fetchMyAPI()
}, [fetchMyAPI])
return (
<div>
<div>data: {JSON.stringify(data)}</div>
<div>
<button onClick={fetchMyAPI}>manual fetch</button>
</div>
</div>
)
}
通过useCallback useCallback。沙盒。
import React, { useState, useEffect, useCallback } from "react";
export default function App() {
const [counter, setCounter] = useState(1);
// if counter is changed, than fn will be updated with new counter value
const fn = useCallback(() => {
setCounter(counter + 1);
}, [counter]);
// if counter is changed, than fn will not be updated and counter will be always 1 inside fn
/*const fnBad = useCallback(() => {
setCounter(counter + 1);
}, []);*/
// if fn or counter is changed, than useEffect will rerun
useEffect(() => {
if (!(counter % 2)) return; // this will stop the loop if counter is not even
fn();
}, [fn, counter]);
// this will be infinite loop because fn is always changing with new counter value
/*useEffect(() => {
fn();
}, [fn]);*/
return (
<div>
<div>Counter is {counter}</div>
<button onClick={fn}>add +1 count</button>
</div>
);
}
useEffect(() => { let unmounted = false promise.then(res => { if (!unmounted) { setState(...) } }) return () => { unmounted = true } }, [])