我有一个useEffect钩子,我在我的App.js文件中使用它。它将数据放入redux store中,我需要在我的应用程序中使用这些数据。但是它在useEffect运行之前就开始渲染了,因此数据是未定义的。然后useEffect正确运行。 我需要在任何东西被渲染之前运行useEffect。我该怎么做?或者我应该使用什么其他解决方案?我已经尝试完全删除useEffect并只运行操作,但结果是它无休止地运行。 这是我的代码:
function App() {
const app = useSelector(state => state.app);
const auth = useSelector(state => state.auth);
const dispatch = useDispatch();
useEffect(() => {
dispatch(authActions.checkUser());
}, [dispatch]);
console.log(auth.user); //undefined
return (
<ThemeProvider theme={!app.theme ? darkTheme : theme}>
<CssBaseline />
<React.Fragment>
{/* TODO: Display drawer only when logged in */}
{/* <Drawer></Drawer> */}
<Switch>
<Route exact path="/" component={Login} />
<Route exact path="/dashboard">
<Dashboard user={auth.user} /> //auth.user is undefined when this gets rendered
</Route>
<Route exact path="/register" component={Register} />
</Switch>
</React.Fragment>
</ThemeProvider>
);
}
export const checkUser = () => async dispatch => {
let token = localStorage.getItem("auth-token");
if (token === null) {
localStorage.setItem("auth-token", "");
token = "";
}
const tokenRes = await Axios.post("http://localhost:5000/users/tokenIsValid", null, {
headers: { "x-auth-token": token }
});
if (tokenRes.data) {
const userRes = await Axios.get("http://localhost:5000/users/", {
headers: { "x-auth-token": token }
});
dispatch({
type: CHECK_USER,
token,
user: userRes.data
});
}
};