Typescript Interface - Possible to make “one or the other” properties required?

Question

Possibly an odd question, but i\'m curious if it\'s possible to make an interface where one property or the other is required.

So, for example...

int         


        

Answer 1

You can use a union type to do this:

interface MessageBasics {
  timestamp?: number;
  /* more general properties here */
}
interface MessageWithText extends MessageBasics {
  text: string;
}
interface MessageWithAttachment extends MessageBasics {
  attachment: Attachment;
}
type Message = MessageWithText | MessageWithAttachment;

If you want to allow both text and attachment, you would write

type Message = MessageWithText | MessageWithAttachment | (MessageWithText & MessageWithAttachment);