React 类组件转换为功能组件（Ant Design）答案

【问题标题】：React class component convert to functional component (Antdesign)React 类组件转换为功能组件（Ant Design）
【发布时间】：2021-10-21 01:38:59
【问题描述】：

我是 React 新手，我想使用 Antdesign 进行图片上传，但在 ant design 的网站上给出了组件类组件。如何将下面的代码转换为功能组件？我可以通过什么方式做到这一点？或者有什么在线工具可以做到这一点？

这是我的代码：

function getBase64(img, callback) {
  const reader = new FileReader();
  reader.addEventListener('load', () => callback(reader.result));
  reader.readAsDataURL(img);
}

function beforeUpload(file) {
  const isJpgOrPng = file.type === 'image/jpeg' || file.type === 'image/png';
  if (!isJpgOrPng) {
    message.error('You can only upload JPG/PNG file!');
  }
  const isLt2M = file.size / 1024 / 1024 < 2;
  if (!isLt2M) {
    message.error('Image must smaller than 2MB!');
  }
  return isJpgOrPng && isLt2M;
}

class Avatar extends React.Component {
  state = {
    loading: false,
  };

  handleChange = info => {
    if (info.file.status === 'uploading') {
      this.setState({ loading: true });
      return;
    }
    if (info.file.status === 'done') {
      // Get this url from response in real world.
      getBase64(info.file.originFileObj, imageUrl =>
        this.setState({
          imageUrl,
          loading: false,
        }),
      );
    }
  };

  render() {
    const { loading, imageUrl } = this.state;
    const uploadButton = (
      <div>
        {loading ? <LoadingOutlined /> : <PlusOutlined />}
        <div style={{ marginTop: 8 }}>Upload</div>
      </div>
    );
    return (
      <Upload
        name="avatar"
        listType="picture-card"
        className="avatar-uploader"
        showUploadList={false}
        action="https://www.mocky.io/v2/5cc8019d300000980a055e76"
        beforeUpload={beforeUpload}
        onChange={this.handleChange}
      >
        {imageUrl ? <img src={imageUrl} alt="avatar" style={{ width: '100%' }} /> : uploadButton}
      </Upload>
    );
  }
}

ReactDOM.render(<Avatar />, mountNode);

【问题讨论】：

标签： reactjs components antd

【解决方案1】：

您需要将类替换为返回 JSX 元素的函数。
您需要重构您的状态以使用useState 挂钩：https://reactjs.org/docs/hooks-state.html

DigitalOcean 在这里有一个很好的指南：https://www.digitalocean.com/community/tutorials/five-ways-to-convert-react-class-components-to-functional-components-with-react-hooks

它最终会如下所示：

function getBase64(img, callback) {
  const reader = new FileReader();
  reader.addEventListener("load", () => callback(reader.result));
  reader.readAsDataURL(img);
}

function beforeUpload(file) {
  const isJpgOrPng = file.type === "image/jpeg" || file.type === "image/png";
  if (!isJpgOrPng) {
    message.error("You can only upload JPG/PNG file!");
  }
  const isLt2M = file.size / 1024 / 1024 < 2;
  if (!isLt2M) {
    message.error("Image must smaller than 2MB!");
  }
  return isJpgOrPng && isLt2M;
}

function Avatar() {
  const [imageUrl, setImageUrl] = useState(null);
  const [loading, setLoading] = useState(false);

  const handleChange = (info) => {
    if (info.file.status === "uploading") {
      setLoading(true)
      return;
    }
    if (info.file.status === "done") {
      // Get this url from response in real world.
      getBase64(info.file.originFileObj, (imageUrl) => {
        setImageUrl(imageUrl);
        setLoading(false);
      });
    }
  };
  const uploadButton = (
    <div>
      {loading ? <LoadingOutlined /> : <PlusOutlined />}
      <div style={{ marginTop: 8 }}>Upload</div>
    </div>
  );
  return (
    <Upload
      name="avatar"
      listType="picture-card"
      className="avatar-uploader"
      showUploadList={false}
      action="https://www.mocky.io/v2/5cc8019d300000980a055e76"
      beforeUpload={beforeUpload}
      onChange={handleChange}
    >
      {imageUrl ? (
        <img src={imageUrl} alt="avatar" style={{ width: "100%" }} />
      ) : (
        uploadButton
      )}
    </Upload>
  );
};

【讨论】：