building-nestjs-apis

name	building-nestjs-apis
description	Builds enterprise NestJS applications with TypeScript, dependency injection, TypeORM, and microservices patterns. Use when creating scalable Node.js backends, REST/GraphQL APIs, or microservices.

NestJS

Quick Start

import { Controller, Get, Module, NestFactory } from '@nestjs/common';

@Controller('health')
class HealthController {
  @Get()
  check() {
    return { status: 'ok' };
  }
}

@Module({ controllers: [HealthController] })
class AppModule {}

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
}
bootstrap();

Features

Feature	Description	Guide
Modules	Dependency injection, providers	MODULES.md
Controllers	Routes, validation, guards	CONTROLLERS.md
Services	Business logic, repositories	SERVICES.md
Database	TypeORM, Prisma integration	DATABASE.md
Auth	Passport, JWT, guards	AUTH.md
Testing	Unit, e2e with Jest	TESTING.md

Common Patterns

Controller with Validation

@Controller('users')
@UseGuards(JwtAuthGuard)
export class UsersController {
  constructor(private readonly usersService: UsersService) {}

  @Get()
  @Roles('admin')
  findAll(@Query() query: PaginationDto) {
    return this.usersService.findAll(query);
  }

  @Get(':id')
  findOne(@Param('id', ParseUUIDPipe) id: string) {
    return this.usersService.findOne(id);
  }

  @Post()
  create(@Body() dto: CreateUserDto) {
    return this.usersService.create(dto);
  }
}

Service with Repository

@Injectable()
export class UsersService {
  constructor(private readonly usersRepo: UsersRepository) {}

  async findAll(query: PaginationDto) {
    const [users, total] = await this.usersRepo.findAllWithCount({
      skip: query.skip,
      take: query.limit,
    });
    return { data: users, total, page: query.page };
  }

  async findOne(id: string) {
    const user = await this.usersRepo.findOne({ where: { id } });
    if (!user) throw new NotFoundException('User not found');
    return user;
  }

  async create(dto: CreateUserDto) {
    const exists = await this..(dto.);
     (exists)   ();
     ..(..(dto));
  }
}

DTO with Validation

export class CreateUserDto {
  @IsEmail()
  email: string;

  @IsString()
  @MinLength(2)
  name: string;

  @IsString()
  @MinLength(8)
  @Matches(/^(?=.*[A-Z])(?=.*\d)/, {
    message: 'Password must contain uppercase and number',
  })
  password: string;

  @IsOptional()
  @IsEnum(UserRole)
  role?: UserRole;
}

Workflows

API Development

1. Create module with nest g module [name]
2. Create controller and service
3. Define DTOs with class-validator
4. Add guards for auth/roles
5. Write unit and e2e tests

Module Structure

@Module({
  imports: [TypeOrmModule.forFeature([User])],
  controllers: [UsersController],
  providers: [UsersService, UsersRepository],
  exports: [UsersService],
})
export class UsersModule {}

Best Practices

Do	Avoid
Use dependency injection	Direct instantiation
Validate with DTOs	Trusting input
Use guards for auth	Auth logic in controllers
Use interceptors for cross-cutting	Duplicating logging/transform
Write unit + e2e tests	Skipping test coverage

Project Structure

src/
├── main.ts
├── app.module.ts
├── common/
│   ├── decorators/
│   ├── guards/
│   ├── interceptors/
│   └── pipes/
├── config/
├── users/
│   ├── users.module.ts
│   ├── users.controller.ts
│   ├── users.service.ts
│   ├── dto/
│   └── entities/
└── auth/
    ├── auth.module.ts
    ├── strategies/
    └── guards/

For detailed examples and patterns, see reference files above.