Use onChange attribute to listen to the switch toggle.

import { Switch } from 'antd';

function handleSwitchToggle(checked) {
  console.log(`switch to ${checked}`);
}

ReactDOM.render(<Switch defaultChecked onChange={handleSwitchToggle} />, mountNode);

ref: https://ant.design/components/switch/

To update the form values use the below code, just put initialValue attribute in Form.item

<Form.Item
        name="switch"
        label="Switch"
        valuePropName="checked"
        initialValue
>
        <Switch checkedChildren="YES" unCheckedChildren="NO" />
</Form.Item>

you can test the code in this playground with antd switch example https://codesandbox.io/s/xiao-yan-qi-ta-zu-jian-antd-4-17-0-alpha-7-forked-00zvbr?file=/index.js:518-691

These two components are working for me.

import React, { useState } from "react";
import { Form, Switch } from 'antd';

const Example1 = () => {
  const [isChecked, setIsChecked] = useState(false);
  const onFinish = (value) => {
    console.log(value)
  }
  return <Form
    name='example-form'
    onFinish={onFinish}
    initialValues={{
      isChecked
    }}
  >
    <Form.Item
      name='isChecked'
      valuePropName='checked'
    >
      <Switch onChange={setIsChecked} />
    </Form.Item>
  </Form>;
};

const Example2 = () => {
  const onFinish = (value) => {
    console.log(value)
  }
  return <Form
    name='example-form'
    onFinish={onFinish}
    initialValues={{
      isChecked: true
    }}
  >
    <Form.Item
      name='isChecked'
      valuePropName='checked'
    >
      <Switch />
    </Form.Item>
  </Form>;
};