我得到这个警告在反应:
index.js:1 Warning: Cannot update a component (`ConnectFunction`)
while rendering a different component (`Register`). To locate the
bad setState() call inside `Register`
我去了堆栈跟踪中指出的位置，并删除了所有设置状态，但警告仍然存在。这可能发生在redux调度?
我的代码:
register.js
class Register extends Component {
render() {
if( this.props.registerStatus === SUCCESS) {
// Reset register status to allow return to register page
this.props.dispatch( resetRegisterStatus()) # THIS IS THE LINE THAT CAUSES THE ERROR ACCORDING TO THE STACK TRACE
return <Redirect push to = {HOME}/>
}
return (
<div style = {{paddingTop: "180px", background: 'radial-gradient(circle, rgba(106,103,103,1) 0%, rgba(36,36,36,1) 100%)', height: "100vh"}}>
<RegistrationForm/>
</div>
);
}
}
function mapStateToProps( state ) {
return {
registerStatus: state.userReducer.registerStatus
}
}
export default connect ( mapStateToProps ) ( Register );
函数，该函数触发了由register.js调用的registerForm组件中的警告
handleSubmit = async () => {
if( this.isValidForm() ) {
const details = {
"username": this.state.username,
"password": this.state.password,
"email": this.state.email,
"clearance": this.state.clearance
}
await this.props.dispatch( register(details) )
if( this.props.registerStatus !== SUCCESS && this.mounted ) {
this.setState( {errorMsg: this.props.registerError})
this.handleShowError()
}
}
else {
if( this.mounted ) {
this.setState( {errorMsg: "Error - registration credentials are invalid!"} )
this.handleShowError()
}
}
}
堆栈跟踪：
TL,博士;
对于我的案例，我修复警告的方法是将useState更改为useRef
react_devtools_backend.js:2574 Warning: Cannot update a component (`Index`) while rendering a different component (`Router.Consumer`). To locate the bad setState() call inside `Router.Consumer`, follow the stack trace as described in https://reactjs.org/link/setstate-in-render
at Route (http://localhost:3000/main.bundle.js:126692:29)
at Index (http://localhost:3000/main.bundle.js:144246:25)
at Switch (http://localhost:3000/main.bundle.js:126894:29)
at Suspense
at App
at AuthProvider (http://localhost:3000/main.bundle.js:144525:23)
at ErrorBoundary (http://localhost:3000/main.bundle.js:21030:87)
at Router (http://localhost:3000/main.bundle.js:126327:30)
at BrowserRouter (http://localhost:3000/main.bundle.js:125948:35)
at QueryClientProvider (http://localhost:3000/main.bundle.js:124450:21)
我所做的上下文的完整代码(从带有// OLD:的行更改为它们上面的行)。然而，这并不重要，只需尝试从useState更改为useRef!!
import { HOME_PATH, LOGIN_PATH } from '@/constants';
import { NotFoundComponent } from '@/routes';
import React from 'react';
import { Redirect, Route, RouteProps } from 'react-router-dom';
import { useAccess } from '@/access';
import { useAuthContext } from '@/contexts/AuthContext';
import { AccessLevel } from '@/models';
type Props = RouteProps & {
component: Exclude<RouteProps['component'], undefined>;
requireAccess: AccessLevel | undefined;
};
export const Index: React.FC<Props> = (props) => {
const { component: Component, requireAccess, ...rest } = props;
const { isLoading, isAuth } = useAuthContext();
const access = useAccess();
const mounted = React.useRef(false);
// OLD: const [mounted, setMounted] = React.useState(false);
return (
<Route
{...rest}
render={(props) => {
// If in indentifying authentication state as the page initially loads, render a blank page
if (!mounted.current && isLoading) return null;
// OLD: if (!mounted && isLoading) return null;
// 1. Check Authentication is one step
if (!isAuth && window.location.pathname !== LOGIN_PATH)
return <Redirect to={LOGIN_PATH} />;
if (isAuth && window.location.pathname === LOGIN_PATH)
return <Redirect to={HOME_PATH} />;
// 2. Authorization is another
if (requireAccess && !access[requireAccess])
return <NotFoundComponent />;
mounted.current = true;
// OLD: setMounted(true);
return <Component {...props} />;
}}
/>
);
};
export default Index;
最小复制示例
我有点困惑到底是什么引发了这个问题，有一个最小的立即可运行的例子帮助我更好地理解它:
index . html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<script src="https://unpkg.com/react@17/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@17/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/@babel/standalone@7.14.7/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function NotMain(props) {
props.setN(1)
return <div>NotMain</div>
}
function Main(props) {
const [n, setN] = React.useState(0)
return <>
<NotMain setN={setN} />
<div>Main {n}</div>
</>
}
ReactDOM.render(
<Main/>,
document.getElementById('root')
);
</script>
</body>
</html>
错误失败:
react-dom.development.js:61警告:在呈现不同的组件(' NotMain ')时不能更新一个组件(' Main ')。要定位' NotMain '内部错误的setState()调用，请按照https://reactjs.org/link/setstate-in-render中描述的堆栈跟踪
后面跟着一个堆栈跟踪:
at NotMain (<anonymous>:16:9)
at Main (<anonymous>:21:31)
假定16:9是props.setN(1)被调用的确切行，但是由于Babel JSX翻译，行号有点混乱。
解决方案和其他答案一样，是这样做的:
function NotMain(props) {
React.useEffect(() => { props.setN(1) }, [])
return <div>NotMain</div>
}
直观地说，我认为这个错误发生的大致原因是:
你不应该从渲染方法中更新状态，否则会导致不同的结果，这取决于React如何渲染事物的内部顺序。
当使用功能组件时，方法是使用钩子。在我们的例子中，useEffect将在渲染完成后运行，所以我们可以从那里开始执行。
当使用类时，这一点变得更加清晰，例如:
在呈现中调用setState是不可避免的
从渲染方法调用React中的setState()
然而，当使用功能组件时，从概念上讲，事情有点复杂，因为组件函数既是呈现，也是设置回调的代码。
如果useEffect不能在您的情况下使用或如果错误不是由于Redux
我使用setTimeout将两个useState变量中的一个重定向到回调队列。
我有一个父组件和一个子组件，每个组件中都有useState变量。解决方案是使用setTimeout来包装useState变量:
setTimeout(() => SetFilterData(data), 0);
在下面的例子
父组件
import ExpenseFilter from '../ExpensesFilter'
function ExpensesView(props) {
const [filterData, SetFilterData] = useState('')
const GetFilterData = (data) => {
// SetFilterData(data);
//*****WRAP useState VARIABLE INSIDE setTimeout WITH 0 TIME AS BELOW.*****
setTimeout(() => SetFilterData(data), 0);
}
const filteredArray = props.expense.filter(expenseFiltered =>
expenseFiltered.dateSpent.getFullYear().toString() === filterData);
return (
<Window>
<div>
<ExpenseFilter FilterYear = {GetFilterData}></ExpenseFilter>
子组件
const ExpensesFilter = (props) => {
const [filterYear, SetFilterYear] = useState('2022')
const FilterYearListener = (event) => {
event.preventDefault()
SetFilterYear(event.target.value)
}
props.FilterYear(filterYear)
return (
