将有状态 React 组件转换为无状态功能组件：如何实现 "componentDidMount" 种功能？

Question

我写了一个小的有状态 React 组件。加载此组件时，在 componentDidMount 方法中，我使用 Kendo UI 在弹出窗口中显示组件的内容 window.

这是我的代码：

export class ErrorDialog extends React.Component {
  constructor(props, context) {
    super(props, context);
    this.errorPopupWindow = null;
    window.addEventListener('resize', this.resizeComponent);
    this.handleWindowKeyDown = this.handleWindowKeyDown.bind(this);
    this.handleButtonCloseWindowOnClick = this.handleButtonCloseWindowOnClick.bind(this);
    this.handleButtonShowDetailsOnClick = this.handleButtonShowDetailsOnClick.bind(this);
    $('#ErrorInformationForm-CloseWindow').focus();
  }

  render() {
    const errorInformation = this.props.errorInformation;
    const baseException = errorInformation.baseException;
    const showExceptionMessage = (typeof baseException !== 'undefined' && typeof baseException === 'object' && baseException !== null
          && typeof baseException.message !== 'undefined' && typeof baseException.message === 'string' && baseException.message !== null
          && baseException.message !== '') ? true : false;
    const baseExceptionMessage = showExceptionMessage ? baseException.message : '';
    const exceptionMessageCss = showExceptionMessage ? 'k-textbox ce-width-100-pct ce-margin-top-5' : 'ce-invisible';
    return(
      <div id="Error-Dialog-Popup" onKeyDown={this.handleWindowKeyDown}>
        <div className="ce-window-body">
          {errorInformation.message}
          <code>
            <textarea readOnly={true} className={exceptionMessageCss} rows="3" defaultValue={baseExceptionMessage} />
          </code>
        </div>
      </div>
    );
  }

  componentDidMount() {
    const errorInformation = this.props.errorInformation;
    const modalWindowTitle = '<span class="ce-width-100-pct ce-app-color-red"><i class="fa ce-fs-1-2-5x fa-times-circle"></i> ' + errorInformation.heading + '</span>';
    $('#Error-Dialog-Popup').kendoWindow({
      actions: [],
      width: 500,
      height: 130,
      visible: true,
      modal: true,
      title: modalWindowTitle,
      resizable: false
    });
    this.resizeComponent();
  }

  resizeComponent() {
  }

  closeWindowIfPossible(evt) {
  }

  handleWindowKeyDown(evt) {
  }

  handleButtonShowDetailsOnClick(evt) {
  }

  handleButtonCloseWindowOnClick(evt) {
  }
}

鉴于此组件不需要维护任何状态，我正在尝试将此组件转换为无状态功能组件。

我纠结的地方是如何实现componentDidMount功能？这是我到目前为止编写的代码：

export const ErrorDialog = (props, context) => {
  const errorInformation = props.errorInformation;
  const baseException = errorInformation.baseException;
  const showExceptionMessage = (typeof baseException !== 'undefined' && typeof baseException === 'object' && baseException !== null
        && typeof baseException.message !== 'undefined' && typeof baseException.message === 'string' && baseException.message !== null
        && baseException.message !== '') ? true : false;
  const baseExceptionMessage = showExceptionMessage ? baseException.message : '';
  const exceptionMessageCss = showExceptionMessage ? 'k-textbox ce-width-100-pct ce-margin-top-5' : 'ce-invisible';

  const resizeComponent = () => {
  }

  const closeWindowIfPossible = (evt) => {
  }

  const handleWindowKeyDown = (evt) => {
  }

  const handleButtonShowDetailsOnClick = (evt) => {
  }

  const handleButtonCloseWindowOnClick = (evt) => {
  }

  const handleComponentOnLoad = (evt) => {
    console.log('comes in onLoad');
    const errorInformation = props.errorInformation;
    const modalWindowTitle = '<span class="ce-width-100-pct ce-app-color-red"><i class="fa ce-fs-1-2-5x fa-times-circle"></i> ' + errorInformation.heading + '</span>';
    $('#Error-Dialog-Popup').kendoWindow({
      actions: [],
      width: 500,
      height: 130,
      visible: true,
      modal: true,
      title: modalWindowTitle,
      resizable: false
    });
    resizeComponent();
  }

  return(
    <div id="Error-Dialog-Popup" onLoad={handleComponentOnLoad} onKeyDown={handleWindowKeyDown}>
      <div className="ce-window-body">
        {errorInformation.message}
        <code>
          <textarea readOnly={true} className={exceptionMessageCss} rows="3" defaultValue={baseExceptionMessage} />
        </code>
      </div>
    </div>
  );
}

起初，我以为我可以在 div 的 onLoad 事件处理程序中实现 componentDidMount 类功能，但是当我尝试这样做时，我注意到事件没有被触发完全没有（然后我阅读了文档，发现我不能真正使用这个事件:)）。

所以我的问题是：

有没有办法在无状态功能组件中实现 componentDidMount 类功能？本质上我需要做的是在 DOM.
在无状态功能组件的情况下，我正在尝试做的是一个有效的场景，还是我应该坚持使用标准组件？

Answer 1

函数式无状态组件没有生命周期方法。在这种情况下，您应该坚持使用标准组件。

来自 React 的 documentation：

These components must not retain internal state, do not have backing instances, and do not have the component lifecycle methods.

Answer 2

他们所说的（以上），但也考虑制作一个有状态的组件容器并将 props/args 传递给无状态的子组件。

Answer 3

在 React 16.8 中，您现在可以使用 State Hooks for functional components. For componentDidMount, it's recommended to use Effect Hooks。

import React, { useState, useEffect } from 'react';

function Example() {
  // Declare a new state variable, which we'll call "count"
  const [count, setCount] = useState(0);

  // Similar to componentDidMount and componentDidUpdate:
  useEffect(() => {
    document.title = `You clicked ${count} times`;
  }, [count]); // Only re-run the effect if count changes)

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

演示：https://codepen.io/rjruizes/pen/yLMZPvR

如果你想让Effect Hook挂载后只运行，使用空数组作为条件：

useEffect(() => {
  document.title = `You clicked ${count} times`;
}, []);

将有状态 React 组件转换为无状态功能组件：如何实现 "componentDidMount" 种功能？

Converting stateful React component to stateless functional component: How to implement "componentDidMount" kind of functionality?

javascript

dom

event-handling

window-load

reactjs