Why does typescript give an error when using a constant for an enum type?

Question

When I try to pass a conatant instead of in-place values for the field below, I get a type error, but if I use an in-place value, everything works fine

import * as z from "zod";

const data = ["1", "2"];

// this way works fine
/*
  age: z.enum<any, [string, ...string[]]>(["1", "2"])
*/

const schema = z.object({
  name: z.number(),
  age: z.enum<any, [string, ...string[]]>(data) // error here
});

and here is how z.enum type look

declare function createZodEnum<U extends string, T extends Readonly<[U, ...U[]]>>(values: T): ZodEnum<Writeable<T>>;

equt · Accepted Answer · 2022-05-30 11:15:23Z

1

Note that T extends Readonly<[U, ...U[]]>, it would require a type like ['foo', 'bar', /* etc */], but not Array<string>.

In your code,

const data = ["1", "2"];

is actually inferred as

const data: Array<string> = ["1", "2"];

You could either

const data = ["1", "2"] as const;

or as the way you've commented out.

Note how the README said

Alternatively, use as const to define your enum values as a tuple of strings. See the const assertion docs for details.

answered May 30, 2022 at 11:15

equt

3222 silver badges9 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

DevOverflow Over a year ago

Yes, I have found already, but anyway thanks!!

Collectives™ on Stack Overflow

Why does typescript give an error when using a constant for an enum type?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related