以类组件而不是钩子的形式获取数据

import React, { Component } from 'react';

class MyComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      data: null,
      loading: true,
      error: null
    };
  }

  componentDidMount() {
    // 在组件挂载后调用，通常用于发送异步请求获取数据
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(data => {
        this.setState({ data, loading: false });
      })
      .catch(error => {
        this.setState({ error, loading: false });
      });
  }

  render() {
    const { data, loading, error } = this.state;

    if (loading) {
      return <div>Loading...</div>;
    }

    if (error) {
      return <div>Error: {error.message}</div>;
    }

    return <div>Data: {data}</div>;
  }
}

export default MyComponent;