ant-design/components/form/demo/form-context.tsx

import React, { useEffect, useRef, useState } from 'react';
import { SmileOutlined, UserOutlined } from '@ant-design/icons';
import { Avatar, Button, Form, Input, InputNumber, Modal, Typography } from 'antd';
import type { FormInstance } from 'antd/es/form';

const layout = {
  labelCol: { span: 8 },
  wrapperCol: { span: 16 },
};
const tailLayout = {
  wrapperCol: { offset: 8, span: 16 },
};

interface UserType {
  name: string;
  age: string;
}

interface ModalFormProps {
  open: boolean;
  onCancel: () => void;
}

// reset form fields when modal is form, closed
const useResetFormOnCloseModal = ({ form, open }: { form: FormInstance; open: boolean }) => {
  const prevOpenRef = useRef<boolean>();
  useEffect(() => {
    prevOpenRef.current = open;
  }, [open]);
  const prevOpen = prevOpenRef.current;

  useEffect(() => {
    if (!open && prevOpen) {
      form.resetFields();
    }
  }, [form, prevOpen, open]);
};

const ModalForm: React.FC<ModalFormProps> = ({ open, onCancel }) => {
  const [form] = Form.useForm();

  useResetFormOnCloseModal({
    form,
    open,
  });

  const onOk = () => {
    form.submit();
  };

  return (
    <Modal title="Basic Drawer" open={open} onOk={onOk} onCancel={onCancel}>
      <Form form={form} layout="vertical" name="userForm">
        <Form.Item name="name" label="User Name" rules={[{ required: true }]}>
          <Input />
        </Form.Item>
        <Form.Item name="age" label="User Age" rules={[{ required: true }]}>
          <InputNumber />
        </Form.Item>
      </Form>
    </Modal>
  );
};

const App: React.FC = () => {
  const [open, setOpen] = useState(false);

  const showUserModal = () => {
    setOpen(true);
  };

  const hideUserModal = () => {
    setOpen(false);
  };

  const onFinish = (values: any) => {
    console.log('Finish:', values);
  };

  return (
    <Form.Provider
      onFormFinish={(name, { values, forms }) => {
        if (name === 'userForm') {
          const { basicForm } = forms;
          const users = basicForm.getFieldValue('users') || [];
          basicForm.setFieldsValue({ users: [...users, values] });
          setOpen(false);
        }
      }}
    >
      <Form {...layout} name="basicForm" onFinish={onFinish}>
        <Form.Item name="group" label="Group Name" rules={[{ required: true }]}>
          <Input />
        </Form.Item>
        <Form.Item
          label="User List"
          shouldUpdate={(prevValues, curValues) => prevValues.users !== curValues.users}
        >
          {({ getFieldValue }) => {
            const users: UserType[] = getFieldValue('users') || [];
            return users.length ? (
              <ul>
                {users.map(user => (
                  <li key={user.name} className="user">
                    <Avatar icon={<UserOutlined />} />
                    {user.name} - {user.age}
                  </li>
                ))}
              </ul>
            ) : (
              <Typography.Text className="ant-form-text" type="secondary">
                ( <SmileOutlined /> No user yet. )
              </Typography.Text>
            );
          }}
        </Form.Item>
        <Form.Item {...tailLayout}>
          <Button htmlType="submit" type="primary">
            Submit
          </Button>
          <Button htmlType="button" style={{ margin: '0 8px' }} onClick={showUserModal}>
            Add User
          </Button>
        </Form.Item>
      </Form>

      <ModalForm open={open} onCancel={hideUserModal} />
    </Form.Provider>
  );
};

export default App;