Question

我建立了一个登录页面，在填写用户名和密码并点击提交按钮时，它会分派基本上转到后端并检查用户名和密码是否有效的操作。我正在使用 React 和 redux，这是我下面的登录页面

login.js（简化版）

import LoginHandle from '../login/LoginHandle'

function userLogin(event) {
  event.preventDefault()
  const username = document.getElementById("username").value
  const password = document.getElementById("password").value
  
  LoginHandle(username, password)

}

const Login = () => {
  return (
    <div className="flex-row align-items-center">
                  <form onSubmit={(e) => userLogin(e)}>
                    <h1>Login</h1>
                    
                      <input id="username" type="email" placeholder="Username" required/>
                 
                      <input id="password" type="password" placeholder="Password" required/>
      
                        <button type="submit" className="px-4">Login</button>
                </form>
    </div>
  )
}

export default Login

LoginHandle.js（简化版）

import {useDispatch, useSelector} from 'react-redux'
import {getLoginStatus} from '../actions/loginAction'


const LoginHandle = (username, password) => {

    const dispatch = useDispatch()
    dispatch(getLoginStatus(username, password))
    const loginState = useSelector(state=> state.loginStatus) 

    if(loginState.loading) {
        console.log("please wait")
    }

    // .... rest of the logic
}

export default LoginHandle

如您所见，我尝试发送操作，然后检查状态以从后端获得确认。但是我收到这个错误

Error: Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen for one of the following reasons:...

我做错了什么？

Answer 1

import {useDispatch, useSelector} from 'react-redux'
import {getLoginStatus} from '../actions/loginAction'

const useLoginHandler = (username, password, submitted) => {
     const dispatch = useDispatch();
     const loginState = useSelector(state=> state.loginStatus)
     // it is better to put the dispatch inside a useEffect rather than outside
     useEffect(() => {
        if(!submitted) {return};
        dispatch(getLoginStatus(username, password))
     }, [username, password, submitted]);


    if(loginState.loading) {
        console.log("please wait")
    }

    // .... rest of the logic
}

export default useLoginHandler

你对钩子的使用是错误的。它不应该在回调函数内。它应该在最高级别。像下面这样的东西。此外，您不应该直接访问 dom 元素，而是使用 useRef 或 useState 来获取值

const Login = () => {
   const [username, setUsername] = useState('');
   const [password, setPassword] = useState('')
   const [submitted, setSubmitted] = useState(false);
   useLoginHandler(username, password, submitted); //custom hook should be used at this level
   return (
      <form onSubmit={(e) => setSubmitted(true)}>
      <input id="username" type="email" placeholder="Username" required onChange={e => setUsername(e.target.value)}/>
          </form>   
   )
}

Answer 2

您在此实现中使用了 2 个钩子 useDispatch & useSelector 并在函数内调用它们，这是无效用法。钩子只能在功能组件内调用。因此，将您的上述实现更改如下应该可以工作：

Login.js

import {useDispatch, useSelector} from 'react-redux'
import {getLoginStatus} from '../actions/loginAction'

const Login = () => {
  
  const dispatch = useDispatch()
  const loginState = useSelector(state=> state.loginStatus) 

  function userLogin(event) {
    event.preventDefault()
    const username = document.getElementById("username").value
    const password = document.getElementById("password").value
  
    dispatch(getLoginStatus(username, password))
  }


  return (
    <div className="flex-row align-items-center">
                  <form onSubmit={(e) => userLogin(e)}>
                    <h1>Login</h1>
                    
                      <input id="username" type="email" placeholder="Username" required/>
                 
                      <input id="password" type="password" placeholder="Password" required/>
      
                        <button type="submit" className="px-4">{loginState.loading ? "Please wait..." : "Login"}</button>
                </form>
    </div>
  )
}

export default Login

注意事项：

直接在功能组件中而不是在功能组件的函数内部调用 useDispatch。然后我们可以在函数内部使用 useDispatch 的结果
在功能组件中调用 useSelector，然后使用输出显示加载以代替按钮中的文本

在 React 中导入组件时出现无效的钩子调用错误

2 个答案: