不能在未挂载的组件上执行React状态更新

问题

我正在React中编写一个应用程序，无法避免一个超级常见的陷阱，即在componentWillUnmount(…)之后调用setState(…)。

我非常仔细地查看了我的代码，并试图在适当的位置放置一些保护子句，但问题仍然存在，我仍然观察到警告。

因此，我有两个问题:

我如何从堆栈跟踪中找出哪个特定的组件和事件处理程序或生命周期钩子对违反规则负责? 好吧，如何修复问题本身，因为我的代码在编写时就考虑到了这个陷阱，并且已经试图防止它，但一些底层组件仍然生成警告。

浏览器控制台

Warning: Can't perform a React state update on an unmounted component.
This is a no-op, but it indicates a memory leak in your application.
To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount
method.
    in TextLayerInternal (created by Context.Consumer)
    in TextLayer (created by PageInternal) index.js:1446
d/console[e]
index.js:1446
warningWithoutStack
react-dom.development.js:520
warnAboutUpdateOnUnmounted
react-dom.development.js:18238
scheduleWork
react-dom.development.js:19684
enqueueSetState
react-dom.development.js:12936
./node_modules/react/cjs/react.development.js/Component.prototype.setState
react.development.js:356
_callee$
TextLayer.js:97
tryCatch
runtime.js:63
invoke
runtime.js:282
defineIteratorMethods/</prototype[method]
runtime.js:116
asyncGeneratorStep
asyncToGenerator.js:3
_throw
asyncToGenerator.js:29

Code

Book.tsx

import { throttle } from 'lodash';
import * as React from 'react';
import { AutoWidthPdf } from '../shared/AutoWidthPdf';
import BookCommandPanel from '../shared/BookCommandPanel';
import BookTextPath from '../static/pdf/sde.pdf';
import './Book.css';

const DEFAULT_WIDTH = 140;

class Book extends React.Component {
  setDivSizeThrottleable: () => void;
  pdfWrapper: HTMLDivElement | null = null;
  isComponentMounted: boolean = false;
  state = {
    hidden: true,
    pdfWidth: DEFAULT_WIDTH,
  };

  constructor(props: any) {
    super(props);
    this.setDivSizeThrottleable = throttle(
      () => {
        if (this.isComponentMounted) {
          this.setState({
            pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
          });
        }
      },
      500,
    );
  }

  componentDidMount = () => {
    this.isComponentMounted = true;
    this.setDivSizeThrottleable();
    window.addEventListener("resize", this.setDivSizeThrottleable);
  };

  componentWillUnmount = () => {
    this.isComponentMounted = false;
    window.removeEventListener("resize", this.setDivSizeThrottleable);
  };

  render = () => (
    <div className="Book">
      { this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }

      <div className={this.getPdfContentContainerClassName()}>
        <BookCommandPanel
          bookTextPath={BookTextPath}
          />

        <div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
          <AutoWidthPdf
            file={BookTextPath}
            width={this.state.pdfWidth}
            onLoadSuccess={(_: any) => this.onDocumentComplete()}
            />
        </div>

        <BookCommandPanel
          bookTextPath={BookTextPath}
          />
      </div>
    </div>
  );

  getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';

  onDocumentComplete = () => {
    try {
      this.setState({ hidden: false });
      this.setDivSizeThrottleable();
    } catch (caughtError) {
      console.warn({ caughtError });
    }
  };
}

export default Book;

AutoWidthPdf.tsx

import * as React from 'react';
import { Document, Page, pdfjs } from 'react-pdf';

pdfjs.GlobalWorkerOptions.workerSrc = `//cdnjs.cloudflare.com/ajax/libs/pdf.js/${pdfjs.version}/pdf.worker.js`;

interface IProps {
  file: string;
  width: number;
  onLoadSuccess: (pdf: any) => void;
}
export class AutoWidthPdf extends React.Component<IProps> {
  render = () => (
    <Document
      file={this.props.file}
      onLoadSuccess={(_: any) => this.props.onLoadSuccess(_)}
      >
      <Page
        pageNumber={1}
        width={this.props.width}
        />
    </Document>
  );
}

更新1:取消可节流功能(仍然没有运气)

const DEFAULT_WIDTH = 140;

class Book extends React.Component {
  setDivSizeThrottleable: ((() => void) & Cancelable) | undefined;
  pdfWrapper: HTMLDivElement | null = null;
  state = {
    hidden: true,
    pdfWidth: DEFAULT_WIDTH,
  };

  componentDidMount = () => {
    this.setDivSizeThrottleable = throttle(
      () => {
        this.setState({
          pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
        });
      },
      500,
    );

    this.setDivSizeThrottleable();
    window.addEventListener("resize", this.setDivSizeThrottleable);
  };

  componentWillUnmount = () => {
    window.removeEventListener("resize", this.setDivSizeThrottleable!);
    this.setDivSizeThrottleable!.cancel();
    this.setDivSizeThrottleable = undefined;
  };

  render = () => (
    <div className="Book">
      { this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }

      <div className={this.getPdfContentContainerClassName()}>
        <BookCommandPanel
          BookTextPath={BookTextPath}
          />

        <div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
          <AutoWidthPdf
            file={BookTextPath}
            width={this.state.pdfWidth}
            onLoadSuccess={(_: any) => this.onDocumentComplete()}
            />
        </div>

        <BookCommandPanel
          BookTextPath={BookTextPath}
          />
      </div>
    </div>
  );

  getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';

  onDocumentComplete = () => {
    try {
      this.setState({ hidden: false });
      this.setDivSizeThrottleable!();
    } catch (caughtError) {
      console.warn({ caughtError });
    }
  };
}

export default Book;

当前回答

const handleClick = async (item: NavheadersType, index: number) => {
    const newNavHeaders = [...navheaders];
    if (item.url) {
      await router.push(item.url);   =>>>> line causing error (causing route to happen)
      // router.push(item.url);  =>>> coreect line
      newNavHeaders.forEach((item) => (item.active = false));
      newNavHeaders[index].active = true;
      setnavheaders([...newNavHeaders]);
    }
  };

2021-02-10 13:44:48

其他回答

来自@ford04的解决方案对我来说不起作用，特别是如果你需要在多个地方使用isMounted(多个useEffect)，建议使用useRef，如下所示:

基本包

"dependencies": 
{
  "react": "17.0.1",
}
"devDependencies": { 
  "typescript": "4.1.5",
}

我的钩子组件

export const SubscriptionsView: React.FC = () => {
  const [data, setData] = useState<Subscription[]>();
  const isMounted = React.useRef(true);

  React.useEffect(() => {
    if (isMounted.current) {
      // fetch data
      // setData (fetch result)

      return () => {
        isMounted.current = false;
      };
    }
  }
});

2021-02-11 20:30:57

我通过提供useEffect钩子中使用的所有参数来解决这个问题

代码报告了该错误:

useEffect(() => {
    getDistrict({
      geonameid: countryId,
      subdistrict: level,
    }).then((res) => {
      ......
    });
  }, [countryId]);

修复后的代码:

useEffect(() => {
    getDistrict({
      geonameid: countryId,
      subdistrict: level,
    }).then((res) => {
      ......
    });
  }, [countryId,level]);

可以看到，问题解决后，我提供了所有的参数(包括水平参数)，应该通过。

2021-07-27 02:47:38

取决于你如何打开你的网页，你可能不会引起挂载。例如使用<Link/>返回到已经挂载在虚拟DOM中的页面，因此需要componentDidMount生命周期中的数据。

2020-12-02 00:53:54

下面是最简单和最紧凑的解决方案(带有解释)，它是一行程序解决方案。

useEffect(() => { return () => {}; }, []);

上面的useEffect()示例返回一个回调函数，触发React在更新状态之前完成其生命周期的卸载部分。

这个非常简单的解决方案就是我们所需要的。此外，它的工作方式也不同于@ford04和@ sfleletche提供的虚构语法。顺便说一下，下面来自@ford04的代码片段是纯虚构语法(@ sflletche、@vinod、@guneetgstar和@Drew Cordano使用了完全相同的虚构语法)。

data =>{<——虚构/虚构语法

someAsyncOperation().then(data => {
    if (isMounted) setState(data);    // add conditional check
  })

我所有的linter和我整个团队的所有linter都不会接受它，他们报告Uncaught SyntaxError: unexpected令牌:'=>'。我感到惊讶的是，竟然没有人知道这个虚构的语法。有谁参与了这个问题的讨论，特别是那些支持他们的人，能不能向我解释一下他们是如何找到对他们有用的解决方案的?

2021-05-27 04:40:08

为jsx组件添加一个引用，然后检查它是否存在

function Book() {
  const ref = useRef();

  useEffect(() => {
    asyncOperation().then(data => {
      if (ref.current) setState(data);
    })
  });

  return <div ref={ref}>content</div>
}

2021-09-10 11:23:49

不能在未挂载的组件上执行React状态更新

推荐文章

最新文章

标签