How can I turn required props into optional props?

I am using Material-UI, I am trying to use the Modal component along with MobX state.

The Modal api says that children and open are the only 2 required props. The problem I am facing is with the children prop since before opening the modal, there’s no children.

This is how it’s been declared on the store:

  modalConfig: {
    open: boolean,
    body?: React.ReactElement
  } = { open: false, body: undefined };

  openDialog (body?: React.ReactElement): void { = true;
    this.modalConfig.body = body;

  closeDialog (): void { = false;
    this.modalConfig.body = undefined;

The component:

import Modal, { ModalProps } from '@material-ui/core/Modal';
import { useStores } from '../useStores';
import { useObserver } from 'mobx-react';

export const MyModal: React.FC<ModalProps> = (props) => useObserver(() => {
  const { uiStore: { modalConfig: { open, body } } } = useStores();

  const { children = body } = props;

//TS2322: Type 'Element | undefined' is not assignable to type 'ReactElement<any, any> | null'.
//Type 'undefined' is not assignable to type 'ReactElement<any, any> | null'.

// The { children } line below, throws the error above.

  return <Modal {...{ ...props, open }}>{ children }</Modal>;

These are the ModalProps from Material-UI that I am using. I want to give the option to another devs, to use the whole props of the modal when they need it.

export interface ModalProps
  extends StandardProps<React.HTMLAttributes<HTMLDivElement>, never, 'children'> {
  BackdropComponent?: React.ElementType<BackdropProps>;
  BackdropProps?: Partial<BackdropProps>;
  children: React.ReactElement;
  closeAfterTransition?: boolean;
  container?: PortalProps['container'];
  disableAutoFocus?: boolean;
  disableBackdropClick?: boolean;
  disableEnforceFocus?: boolean;
  disableEscapeKeyDown?: boolean;
  disablePortal?: PortalProps['disablePortal'];
  disableRestoreFocus?: boolean;
  disableScrollLock?: boolean;
  hideBackdrop?: boolean;
  keepMounted?: boolean;
  manager?: ModalManager;
  onBackdropClick?: React.ReactEventHandler<{}>;
   * Callback fired when the component requests to be closed.
   * @param {object} event The event source of the callback.
   * @param {string} reason Can be: `"escapeKeyDown"`, `"backdropClick"`.
  onClose?: {
    bivarianceHack(event: {}, reason: 'backdropClick' | 'escapeKeyDown'): void;
  onEscapeKeyDown?: React.ReactEventHandler<{}>;
  onRendered?: PortalProps['onRendered'];
  open: boolean;

And this is how I call it:

//Type '{}' is missing the following properties from type 'ModalProps': children, opents(2739)

// When I call it I get the error above.
<MyModal />

What do you think? Any ideas on how to make it work?

162 thoughts on “How can I turn required props into optional props?”

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