关闭反应模式

Question

我在试图弄清楚如何向我的模态添加一个功能正常的关闭按钮时遇到了很多问题 - 构造函数/道具没有工作，我不确定在按钮元素中的 onClick= 之后放什么。

class Modal extends React.Component {

// whenever component gets rendered to the screen we create a new div assigned to this.modalTarget
	componentDidMount() {
		this.modalTarget = document.createElement('div');
		// add class name to modal target
		this.modalTarget.className = 'modal';
		// take the div we just created and append it to the body tag in doc
		document.body.appendChild(this.modalTarget);
		// call method _render
		this._render();
	}

// whenever the component's about to update we do another render
// this render makes sure that if we get a new set of components or children in the modal
// we're going to render those to the parent div as well
	componentWillUpdate() {
		this._render();
	}

// clean up - whenever the component is about to unmount from the screen
// cleans up dom when the modal is removed from the component heirarchy
	componentWillUnmount() {
		// unmounts this.props.children
		ReactDOM.unmountComponentAtNode(this.modalTarget);
		document.body.removeChild(this.modalTarget);
	}

	_render() {
		// take react dom library and render a div that contains this.props.children
		// and render it into this.modalTarget
		ReactDOM.render(
			<Provider store= {store}>
				<Router>
					<div className="modal">
						{this.props.children}
						<button>Close</button>
					</div>
				</Router>
			</Provider>,
			this.modalTarget

Answer 1

这里有几个问题。首先，远离直接操作DOM. React 使用 virtual DOM，因此您无需手动添加或删除DOM元素。ReactDOM通过render方法自动处理这种操作。此外，您需要Modal使用某种state（isOpen）来控制它。它可以通过 React 的本地状态或通过 Redux 的状态。无论哪种方式，都需要对其进行控制和比较。简而言之，如果它是打开的，渲染Modal，如果它关闭，渲染null。

此外，该Modal组件可以构建为可重用的。只需将它作为一个添加child到另一个有状态parent组件，并在其中包含children您想要呈现的任何内容。

工作示例：

components/Example.js（父组件）

import React, { Component } from "react";
import Modal from "../Modal";
import "./styles.css";

class Example extends Component {
  state = { isOpen: false };

  handleOpenModal = () => {
    this.setState({ isOpen: true });
  };

  handleCloseModal = () => {
    this.setState({ isOpen: false });
  };

  render = () => (
    <div className="example">
      <h2>Simple Modal Example</h2>
      <button
        className="uk-button uk-button-primary uk-button-small"
        onClick={this.handleOpenModal}
      >
        Open Modal
      </button>
      <Modal isOpen={this.state.isOpen} onCloseModal={this.handleCloseModal}>
        <h1 className="title">Hello!</h1>
        <p className="subtitle">There are two ways to close this modal</p>
        <ul>
          <li>Click outside of this modal in the grey overlay area.</li>
          <li>Click the close button below.</li>
        </ul>
        <button
          className="uk-button uk-button-danger uk-button-small"
          onClick={this.handleCloseModal}
        >
          Close
        </button>
      </Modal>
    </div>
  );
}

export default Example;

components/Modal.js（子组件——它有很多较小的组件，为了可重用性和易于理解而分开——它们基本上是简单div的，带有一些styles附件——见下面的注释）

import React from "react";
import PropTypes from "prop-types";
import BackgroundOverlay from "../BackgroundOverlay"; // grey background
import ClickHandler from "../ClickHandler"; // handles clicks outside of the modal
import Container from "../Container"; // contains the modal and background
import Content from "../Content"; // renders the "children" placed inside of <Modal>...</Modal>
import ModalContainer from "../ModalContainer"; // places the modal in the center of the page

// this is a ternary operator (shorthand for "if/else" -- if cond ? then : else)
// below can be read like: if isOpen is true, then return/render the modal, else return null
const Modal = ({ children, isOpen, onCloseModal }) =>
  isOpen ? (
    <Container>
      <BackgroundOverlay />
      <ModalContainer>
        <ClickHandler isOpen={isOpen} closeModal={onCloseModal}>
          <Content>{children}</Content>
        </ClickHandler>
      </ModalContainer>
    </Container>
  ) : null;

// these proptype declarations are to ensure that passed down props are 
// consistent and are defined as expected
Modal.propTypes = {
  children: PropTypes.node.isRequired, // children must be a React node
  isOpen: PropTypes.bool.isRequired, // isOpen must be a boolean
  onCloseModal: PropTypes.func.isRequired // onCloseModal must be a function
};

export default Modal;