CODEWITHSUNDEEP
typescripttypescript2.0
Alexander Mills
Alexander Mills

Reputation: 100130

Declare current module as having a particular interface

I have a project with a folder in it, each with a module that should have a particular interface:

project/
  modules/
    A/index.ts
    B/index.ts
    C/index.ts

each of the index.ts files, should adhere to a certain interface. Something like this:

export const foo = ...
export const bar = ...

how can I declare that each index.ts file must export a certain interface? In other words, I need to tell TypeScript that module.exports for each of these index.ts files must adhere to a certain interface.

I filed an issue for this with TypeScript / DefinitelyTyped on Github: https://github.com/Microsoft/TypeScript/issues/19554

Upvotes: 0

Views: 223

Answers (1)

Aluan Haddad
Aluan Haddad

Reputation: 31833

In general, specifying types that modules must implement is not yet supported, but you can use a convention such as you suggested in the GitHub issue that you linked from.

Well, it actually does work with export forms but you are using invalid export syntax (export {} as MyInterface) irrespective of the presence of types.

One way to write this would be

export interface MyInterface {
    id: number;
    name:string
}

const m: MyInterface = {
    id: 1
}

export = m;

We might think to write it more concisely as

export = {id: 1} as MyInterface;

which is valid syntax but acts as a type assertion, not an implementation requirement, such that

export = {} as MyInterface;

typechecks as well. This makes the first form preferable.

Upvotes: 1

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