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:


当前回答

我认为这很重要。 @Red-Baron在这篇文章中指出:

@machineghost:我认为你误解了这条信息警告的内容。

将更新父节点状态的回调传递给子节点并没有什么错。这一直都很好。

问题是当一个组件在另一个组件中排队更新时,而第一个组件正在呈现。

换句话说,不要这样做:

function SomeChildComponent(props) {
    props.updateSomething();
    return <div />
}

但这是可以的:

function SomeChildComponent(props) {
    // or make a callback click handler and call it in there
    return <button onClick={props.updateSomething}>Click Me</button>
}

而且,正如Dan多次指出的那样,在渲染时在同一个组件中排队更新也很好:

function SomeChildComponent(props) {
  const [number, setNumber] = useState(0);

  if(props.someValue > 10 && number < 5) {
    // queue an update while rendering, equivalent to getDerivedStateFromProps
    setNumber(42);
  }

  return <div>{number}</div>
}

其他回答

我通过将分配从寄存器组件渲染方法移除到componentwillunmount方法来修复这个问题。这是因为我希望这个逻辑在重定向到登录页面之前发生。一般来说,最好的做法是把所有的逻辑都放在渲染方法之外,所以我的代码之前写得很糟糕。希望这能在将来对其他人有所帮助:)

我重构的寄存器组件:

class Register extends Component {

  componentWillUnmount() {
    // Reset register status to allow return to register page
    if ( this.props.registerStatus !== "" ) this.props.dispatch( resetRegisterStatus() )
  }

  render() {
    if( this.props.registerStatus === SUCCESS ) { 
      return <Redirect push to = {LOGIN}/>
    }
    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>
    );
  }
}

此警告从React V16.3.0开始引入。

如果您正在使用功能组件,您可以将setState调用包装到useEffect中。

不能工作的代码:

const HomePage = (props) => {
    
  props.setAuthenticated(true);

  const handleChange = (e) => {
    props.setSearchTerm(e.target.value.toLowerCase());
  };

  return (
    <div key={props.restInfo.storeId} className="container-fluid">
      <ProductList searchResults={props.searchResults} />
    </div>
  );
};

现在你可以把它改成:

const HomePage = (props) => {
  // trigger on component mount
  useEffect(() => {
    props.setAuthenticated(true);
  }, []);

  const handleChange = (e) => {
    props.setSearchTerm(e.target.value.toLowerCase());
  };

  return (
    <div key={props.restInfo.storeId} className="container-fluid">
      <ProductList searchResults={props.searchResults} />
    </div>
  );
};

如果你使用React导航并且你正在使用setParams或setOptions,你必须把这些放在类组件的componentDidMount()方法中或函数组件的useEffects()钩子中。

我的例子。

带有错误的代码:

<Form
    initialValues={{ ...kgFormValues, dataflow: dataflows.length > 0 ? dataflows[0].df_tpl_key : "" }}
    onSubmit={() => {}}
    render={({values, dirtyFields }: any) => {
      
      const kgFormValuesUpdated = {
        proj_key: projectKey,
        name: values.name,
        description: values.description,
        public: values.public,
        dataflow: values.dataflow,
        flavours: flavoursSelected,
        skipOCR: values.skipOCR
      };

      if (!_.isEqual(kgFormValues, kgFormValuesUpdated)) {
        setNewKgFormValues(kgFormValuesUpdated);
      }

工作代码:

 <Form
    initialValues={{ ...kgFormValues, dataflow: dataflows.length > 0 ? dataflows[0].df_tpl_key : "" }}
    onSubmit={() => {}}
    render={({ values, dirtyFields }: any) => {
      useEffect(() => {
        const kgFormValuesUpdated = {
          proj_key: projectKey,
          name: values.name,
          description: values.description,
          public: values.public,
          dataflow: values.dataflow,
          flavours: flavoursSelected,
          skipOCR: values.skipOCR
        };

        if (!_.isEqual(kgFormValues, kgFormValuesUpdated)) {
          setNewKgFormValues(kgFormValuesUpdated);
        }
      }, [values]);

      return (

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 (