api.user.controller.ts

class APIUserController {
  constructor(private service: UserService) {}

  update(): void {
    const id = 4;
    const name = "Nicolás";

    this.service.setUserName(id, name);
  }

  show(): void {
    const name = this.service.getUserName(4);
  }
}

user.model.ts

class User {
  constructor(private name: string) {}

  static findById(id: number): User {
    return new User("Nico");
  }

  getName(): string {
    return this.name;
  }

  setName(name: string): void {
    this.name = name;
  }
}

user.repository.ts

class UserRepository {
  updateUserName(id: number, name: string): void {
    const user = User.findById(id);

    user.setName(name);

    // persistir cambios
  }

  getUserName(id: number): string {
    return User.findById(id).getName();
  }
}

user.service.ts

class UserService {
  constructor(private repo: UserRepository) {}

  private ensureNonEmptyName(name: string): void {
    if (!name.trim()) {
      throw new Error("Name cannot be empty");
    }
  }

  setUserName(id: number, name: string): void {
    this.ensureNonEmptyName(name);

    this.repo.updateUserName(id, name);
  }

  getUserName(id: number): string {
    return this.repo.getUserName(id);
  }
}