ant-design/components/switch/index.tsx

import RcSwitch from 'rc-switch';
import * as React from 'react';
import classNames from 'classnames';

export default class Switch extends React.Component {
  static defaultProps = {
    prefixCls: 'ant-switch',
  }

  render() {
    const { prefixCls, size, className } = this.props;
    const cls = classNames({
      [className]: !!className,
      [`${prefixCls}-small`]: size === 'small',
    });
    return <RcSwitch className={cls} {...this.props} />;
  }
}