使用 useEffect() 重定向不起作用？

Question

如果登录成功并且令牌存储在 localStorage 中，我应该被重定向到私有路由，即 /panel。如果没有，我应该显示来自 ShowError() 的错误消息。

目前，如果登录不成功，则会显示我的错误消息，所以一切都很好。但是，如果存在令牌，则仍然没有重定向。

function LoginPage (){
  const [state, setState] = useState({
    email: '',
    password: '',
  }); 

 const [submitted, setSubmitted] = useState(false);
 const [shouldRedirect, setShouldRedirect] = useState(false);

function ShowError(){
  if (!localStorage.getItem('token'))
  {
    console.log('Login Not Successful');
    return (
      <ThemeProvider theme={colortheme}>
    <Typography color='primary'>
      Login Unsuccessful
      </Typography>
      </ThemeProvider>)
  }
}

// function FormSubmitted(){
//   setSubmitted(true);
//   console.log('Form submitted');
// }

// function RedirectionToPanel(){
//   console.log('check');
//   if(submitted && localStorage.getItem('token')){
//     console.log('Finall');
//     return <Redirect to='/panel'/>
//   }
// }

useEffect(() => {
    if(localStorage.getItem('token')){
      setShouldRedirect(true);
    }
  },[] );


  function submitForm(LoginMutation: any) {
    setSubmitted(true);
    const { email, password } = state;
    if(email && password){
      LoginMutation({
        variables: {
            email: email,
            password: password,
        },
    }).then(({ data }: any) => {
      localStorage.setItem('token', data.loginEmail.accessToken);
    })
    .catch(console.log)
    }
  }
    return (
      <Mutation mutation={LoginMutation}>
        {(LoginMutation: any) => (
          <Container component="main" maxWidth="xs">
            <CssBaseline />
            <div style={{
              display: 'flex',
              flexDirection: 'column',
              alignItems: 'center'
            }}>
              <Avatar>
                <LockOutlinedIcon />
              </Avatar>
              <Typography component="h1" variant="h5">
                Sign in
              </Typography>
              <Formik
                initialValues={{ email: '', password: '' }}
                onSubmit={(values, actions) => {
                  setTimeout(() => {
                    alert(JSON.stringify(values, null, 2));
                    actions.setSubmitting(false);
                  }, 1000);
                }}
                validationSchema={schema}
              >
                {props => {
                  const {
                    values: { email, password },
                    errors,
                    touched,
                    handleChange,
                    isValid,
                    setFieldTouched
                  } = props;
                  const change = (name: string, e: any) => {
                    e.persist();                
                    handleChange(e);
                    setFieldTouched(name, true, false);
                    setState( prevState  => ({ ...prevState,   [name]: e.target.value }));  
                  };
                  return (
                    <form style={{ width: '100%' }} 
                    onSubmit={e => {e.preventDefault();
                    submitForm(LoginMutation);}}>
                      <TextField
                        variant="outlined"
                        margin="normal"
                        id="email"
                        fullWidth
                        name="email"
                        helperText={touched.email ? errors.email : ""}
                        error={touched.email && Boolean(errors.email)}
                        label="Email"     
                        value={email}
                        onChange={change.bind(null, "email")}
                      />
                      <TextField
                        variant="outlined"
                        margin="normal"
                        fullWidth
                        id="password"
                        name="password"
                        helperText={touched.password ? errors.password : ""}
                        error={touched.password && Boolean(errors.password)}
                        label="Password"
                        type="password"
                        value={password}
                        onChange={change.bind(null, "password")}
                      /> 
                      {submitted && ShowError()}

                      <FormControlLabel
                        control={<Checkbox value="remember" color="primary" />}
                        label="Remember me"
                      />
                      <br />
                      <Button className='button-center'
                        type="submit"
                        disabled={!isValid || !email || !password}
                        // onClick={handleOpen}
                        style={{
                          background: '#6c74cc',
                          borderRadius: 3,
                          border: 0,
                          color: 'white',
                          height: 48,
                          padding: '0 30px'
                        }}
                      >                       
                        Submit</Button>
                      <br></br>
                      <Grid container>
                        <Grid item xs>
                          <Link href="#" variant="body2">
                            Forgot password?
                          </Link>
                        </Grid>
                        <Grid item>
                          <Link href="#" variant="body2">
                            {"Don't have an account? Sign Up"}
                          </Link>
                        </Grid>                    
                      </Grid>
                    </form>
                  )
                }}
              </Formik>
            </div>
            <Box mt={8}>
              <Copyright />
            </Box>
            {/* {submitted && <Redirect to='/panel'/>} */}
          </Container>
          )
        }
      </Mutation>
    );
}

export default LoginPage;

我的 App.tsx：

const token = localStorage.getItem('token');

const PrivateRoute = ({component, isAuthenticated, ...rest}: any) => {
  const routeComponent = (props: any) => (
      isAuthenticated
          ? React.createElement(component, props)
          : <Redirect to={{pathname: '/404'}}/>
  );
  return <Route {...rest} render={routeComponent}/>;
};

export default function App() {
  return (
    <div>
      <BrowserRouter>
      <Switch>
      <Route exact path='/' component= {HomePage}></Route>
      <Route path='/login' component= {LoginPage}></Route>
      <Route path='/404' component= {Error404Page}></Route>
      <PrivateRoute
      path='/panel'
      isAuthenticated={token}
      component={PanelHomePage}
      />
      <Redirect from='*' to='/404' />
      </Switch>
      </BrowserRouter>
    </div>
  );
}

Answer 1

为什么要使用 useState 来重定向？直接重定向就好了。如果您使用的是react-router，最好使用useHistory。

import { useHistory } from 'react-router-dom';

const history = useHistory();
useEffect(() => {
    if(localStorage.getItem('token')){
      history.push({
        pathname: '/',
      });
    }
},[]);

如果你仍然想使用 useState，你可以创建一个新的 useEffect NS 将该状态添加到你的依赖数组中。

const history = useHistory();
useEffect(() => {
    if(localStorage.getItem('token')){
      setShouldRedirect(true);
    }
},[]);

useEffect(() => {
  if(shouldRedirect){
    history.push({
      pathname: '/',
    });
  }
},[shouldRedirect]);