@Injectable
export class UsersService {
  constructor(private readonly usersRepository: UsersRepository, private readonly hashPasswordService: HashPasswordService) {}

  public async createUser(createUserRequest: CreateUserRequest) : Promise<UserResponse> {
      const user = new UserEntity();
      //...
      user.hashedPassword = await this.hashPasswordService.hash(createUserRequest.password)
      //...

     await this.usersRepository.save(user);
     //...
     return userResponse;
  }
}

@Injectable
export class UserEventsListener implements EntitySubscriberInterface<User> {
  constructor(@InjectConnection() private readonly connection: Connection, private readonly hashPasswordService: HashPasswordService) {
    connection.subscribers.push(this);
  }

  public listenTo() {
    return User;
  }

  public async beforeInsert(event: InsertEvent<User>): Promise<void> {
    event.entity.password = await this.hashPasswordService.hash(event.entity.password);
  }
}