Can I use a TypeScript type with io-ts?

Question

I am working on validating API responses using io-ts.

I have already defined the following type in regular TypeScript:

export type Group = {
   id: number;
   name: string;
}

And I want to use this type in io-ts like this:

const UploadedSearch = t.type({
    id: t.number,
    title: t.string,
    groups: t.array(Group),
});

But I get the following error.

TS2693: 'Group' only refers to a type, but is being used as a value here.

Is there any way to use Group in the io-ts code?

you must make a new type. – not my real name Mar 28 '20 at 23:13 — not my real name, Mar 28 '20 at 23:13

score 4 · Accepted Answer · answered Oct 04 '20 at 04:32

The comment on your question already mentioned this but to illustrate how to use io-ts not to repeat yourself, you can say:

const GroupCodec = t.type({
  id: t.number,
  name: t.string,
});
// Will be equivalent to your group type, so no need to repeat yourself.
export type Group = t.TypeOf<typeof GroupCodec>;

const UploadedSearch = t.type({
  id: t.number,
  title: t.string,
  groups: t.array(GroupCodec),
});

Can I use a TypeScript type with io-ts?

1 Answers1