CODEWITHSUNDEEP
typescript
Bart van den Burg
Bart van den Burg

Reputation: 2344

Encapsulate intersect type into interface

I see myself writing the following everywhere:

product: Product & { id: string; };

How do I write an interface, so that instead I can write

product: WithId<Product>;

I tried something like this, but the compiler doesn't like extending from generics:

export interface WithId<T> extends T {
    id: string;
}

Upvotes: 2

Views: 46

Answers (2)

Maciej Sikora
Maciej Sikora

Reputation: 20162

You can abstract the construct by abstraction of & {id: string}

export type WithId<T> = T & { id: string }

type Example = WithId<{ a: number }> // {a: number, id: string}
const example: Example = {a: 1, id: 'id'}

PS. { [K in keyof T]: T[keyof T] } is nothing different like T itself, so redundant.

Upvotes: 2

Murat Karag&#246;z
Murat Karag&#246;z

Reputation: 37604

You can use a type intersection

export type WithId<T> = { [K in keyof T]: T[keyof T] } & { id: string }


interface product { myNew: string }
let et: WithId<product> = { myNew: "s", id: "s" } // ok
let et: WithId<product> = { test: "s", id: "s" } // error

Upvotes: 0

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