حقن التبعية (DI) وحاويات IoC

// بدون DI - اقتران قوي
class Logger {
  log(message: string) { /* ... */ }
}

class UserService {
  private logger = new Logger(); // إنشاء داخلي - اقتران
}

// مع DI - اقتران ضعيف
class UserService {
  constructor(private logger: Logger) {} // حقن من الخارج
}

import { Container, injectable, inject } from "inversify";

const container = new Container();

@injectable()
class Logger {
  log(message: string) {
    console.log(`[LOG]: ${message}`);
  }
}

@injectable()
class UserService {
  constructor(@inject(Logger) private logger: Logger) {}

  createUser(name: string) {
    this.logger.log(`إنشاء مستخدم: ${name}`);
  }
}

container.bind(Logger).toSelf();
container.bind(UserService).toSelf();

@Injectable()
export class UsersService {
  constructor(
    @InjectRepository(User)
    private usersRepository: Repository<User>,
    private mailService: MailService,
  ) {}

  async create(dto: CreateUserDto) {
    const user = this.usersRepository.save(dto);
    await this.mailService.sendWelcome(user);
    return user;
  }
}

// Constructor Injection
class Service {
  constructor(private dep: Dependency) {}
}

// Property Injection
class Service {
  @inject(Dependency) private dep!: Dependency;
}

// Method Injection
class Service {
  setDependency(dep: Dependency) {
    this.dep = dep;
  }
}