TypeScript and Swagger: create a generic GetManyAndCount class definition

I've a collection of Item objects. From a REST API (using Node.js and Nest.js), I'm returning many objects and a count of all available objects in the database:

type Response = {
  many: Item[];
  count: number;
}

I'm also using Swagger and a TypeScript codebase (I'm using Nest.js and its Swagger plugin).

Here, instead of using the Response type, I want to specify a class definition as a returned type on my API controller (: Promise<GetManyItemsAndCountDto>), so the API response is automatically documented in the Swagger schema:

export class GetManyItemsAndCountDto extends GetManyAndCountType(Item) {}

export class ItemsController {
  async getItems(/* ... */): Promise<GetManyItemsAndCountDto> {
    // ...
  }
}

Like here, in my project all APIs returning a collection of objects, are also returning a count.

How I can define correctly a generic and reusable GetManyAndCountType() class/function to get the response definition correctly documented with Swagger?

What I've tried:

• I tried the solution below using a mixin (inspired by another use case). The GetManyItemsAndCountDto is well created in the swagger json schema, but only as an "object" without its 2 properties: many: Items[] and count: number, which is useless.

interface IGetManyAndCount<T> {
  many: T[];
  count: number;
}

export function GetManyAndCountType<T>(ResourceClass) {
  return class GetManyAndCount implements IGetManyAndCount<T> {
    many: typeof ResourceClass[];
    count: number;
  };
}

export class GetManyItemsAndCountDto extends GetManyAndCountType(Items) {}

• For the time being, the only working solution I have is to create explicitly a class GetManyItemsAndCountDto (but I would like to find a more generic solution to avoid code duplication on several similar situations and APIs I have):

export class GetManyItemsAndCountDto {
  many: Item[];
  count: number;
}

Thanks in advance for any help or comments.