AgentSkillsCN

NestJS Patterns

以 NestJS 框架构建可扩展 Node.js 应用程序的全面模式，涵盖模块、提供者、控制器以及企业级设计模式。

SKILL.md
--- frontmatter
name: NestJS Patterns
description: Comprehensive patterns for building scalable Node.js applications with NestJS framework including modules, providers, controllers, and enterprise patterns.

NestJS Patterns

Overview

NestJS เป็น progressive Node.js framework ที่ใช้ TypeScript เป็นหลัก ออกแบบมาสำหรับ building scalable server-side applications โดยใช้ architectural patterns จาก Angular รวมถึง Dependency Injection, Modules, และ Decorators

Why This Matters

  • •Scalability: Modular architecture ทำให้จัดการ codebase ขนาดใหญ่ได้ง่าย
  • •Type Safety: Built-in TypeScript support ลด runtime errors
  • •Enterprise Ready: มี patterns สำหรับ microservices, GraphQL, WebSocket out-of-the-box
  • •Testability: DI system ทำให้ unit testing ง่าย

Core Concepts

1. Module Architecture

typescript
// feature.module.ts
@Module({
  imports: [DatabaseModule, CacheModule],
  controllers: [FeatureController],
  providers: [FeatureService, FeatureRepository],
  exports: [FeatureService], // expose to other modules
})
export class FeatureModule {}

Best Practices:

  • •แบ่ง module ตาม domain/feature
  • •ใช้ shared module สำหรับ common utilities
  • •Export เฉพาะ services ที่จำเป็น

2. Dependency Injection

typescript
// ใช้ constructor injection
@Injectable()
export class OrderService {
  constructor(
    private readonly orderRepo: OrderRepository,
    private readonly paymentService: PaymentService,
    @Inject('CONFIG') private config: AppConfig,
  ) {}
}

// Custom providers
const configProvider = {
  provide: 'CONFIG',
  useFactory: (configService: ConfigService) => configService.get('app'),
  inject: [ConfigService],
};

3. Controllers & DTOs

typescript
@Controller('orders')
@UseGuards(JwtAuthGuard)
export class OrderController {
  @Post()
  @HttpCode(HttpStatus.CREATED)
  async create(
    @Body() dto: CreateOrderDto,
    @CurrentUser() user: User,
  ): Promise<OrderResponseDto> {
    return this.orderService.create(dto, user.id);
  }

  @Get(':id')
  @UseInterceptors(CacheInterceptor)
  async findOne(@Param('id', ParseUUIDPipe) id: string) {
    return this.orderService.findOne(id);
  }
}

4. Exception Handling

typescript
// Custom exception filter
@Catch()
export class AllExceptionsFilter implements ExceptionFilter {
  catch(exception: unknown, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();
    
    const status = exception instanceof HttpException
      ? exception.getStatus()
      : HttpStatus.INTERNAL_SERVER_ERROR;

    const message = exception instanceof HttpException
      ? exception.message
      : 'Internal server error';

    response.status(status).json({
      statusCode: status,
      message,
      timestamp: new Date().toISOString(),
    });
  }
}

5. Interceptors & Pipes

typescript
// Transform response interceptor
@Injectable()
export class TransformInterceptor<T> implements NestInterceptor<T, Response<T>> {
  intercept(context: ExecutionContext, next: CallHandler): Observable<Response<T>> {
    return next.handle().pipe(
      map(data => ({
        success: true,
        data,
        timestamp: new Date().toISOString(),
      })),
    );
  }
}

// Validation pipe (global)
app.useGlobalPipes(new ValidationPipe({
  whitelist: true,
  forbidNonWhitelisted: true,
  transform: true,
}));

Quick Start

  1. •

    Create new project:

    bash
    nest new my-project
cd my-project
  2. •

    Generate resources:

    bash
    nest g module users
nest g controller users
nest g service users
  3. •

    Setup validation:

    bash
    npm install class-validator class-transformer
  4. •

    Configure global pipes in main.ts:

    typescript
    app.useGlobalPipes(new ValidationPipe({ whitelist: true }));
  5. •

    Add Swagger documentation:

    bash
    npm install @nestjs/swagger swagger-ui-express

Production Checklist

  • • Global exception filter configured
  • • Validation pipes enabled globally
  • • Health check endpoint (/health)
  • • Swagger documentation enabled (dev only)
  • • Rate limiting configured
  • • Helmet security headers
  • • CORS properly configured
  • • Environment config validated on startup
  • • Graceful shutdown handling
  • • Request logging with correlation IDs

Anti-patterns

  1. •Fat Controllers: Controllers should only handle HTTP concerns, delegate logic to services
  2. •Circular Dependencies: Use forwardRef() sparingly, refactor module structure instead
  3. •Skipping DTOs: Always validate input with DTOs and class-validator
  4. •God Modules: Break large modules into smaller, focused modules

Integration Points

  • •Database: @nestjs/typeorm, @nestjs/mongoose, @nestjs/prisma
  • •Caching: @nestjs/cache-manager with Redis
  • •Queue: @nestjs/bull for job processing
  • •GraphQL: @nestjs/graphql with Apollo
  • •Microservices: @nestjs/microservices for distributed systems

Further Reading