Code Quiz

Domain Layer DTO Leak

A layered RN use case returns a raw data-layer DTO instead of a mapped domain entity.

Codetypescript

// data/UserApi.ts
export interface UserDTO {
  user_id: string;
  first_name: string;
  last_name: string;
}

export class UserApi {
  async fetchUser(id: string): Promise<UserDTO> {
    const res = await fetch(`/api/users/${id}`);
    return res.json();
  }
}

// domain/GetUserProfile.ts
import { UserApi, UserDTO } from '../data/UserApi';

export interface UserProfile {
  id: string;
  fullName: string;
}

export class GetUserProfile {
  constructor(private api = new UserApi()) {}

  async execute(id: string): Promise<UserProfile> {
    const dto: UserDTO = await this.api.fetchUser(id);
    return dto as unknown as UserProfile;
  }
}

What is the architectural bug in this use case?

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