Tutorial: CRUD REST module in NestJS

NestJS gives structure to Node APIs with modules, controllers, and providers. This tutorial builds a small CRUD API you can swap to a real database later.

What you will build

• A `TasksModule` with controller, service, and DTOs
• `GET /tasks`, `POST /tasks`, `PATCH /tasks/:id`, `DELETE /tasks/:id`
• Validation via `class-validator` and global `ValidationPipe`

Prerequisites

• Node.js 20+
• Nest CLI: `npm i -g @nestjs/cli`
• Basic REST and TypeScript

Step-by-step

1. Run `nest new tasks-api` and `cd tasks-api`.
2. Generate a resource: `nest g resource tasks --no-spec`, choose REST and no Swagger for now.
3. Define `CreateTaskDto` and `UpdateTaskDto` with `class-validator` decorators (`@IsString`, `@IsOptional`).
4. Enable `app.useGlobalPipes(new ValidationPipe({ whitelist: true }))` in `main.ts`.
5. Implement service methods with an in-memory array; use UUIDs from `crypto.randomUUID()`.
6. Test endpoints with curl or the REST Client VS Code extension.

DTO example

import { IsOptional, IsString, MinLength } from "class-validator";

export class CreateTaskDto {
  @IsString()
  @MinLength(2)
  title: string;

  @IsOptional()
  @IsString()
  description?: string;
}

Controller routes

@Controller("tasks")
export class TasksController {
  constructor(private readonly tasksService: TasksService) {}

  @Get()
  findAll() {
    return this.tasksService.findAll();
  }

  @Post()
  create(@Body() dto: CreateTaskDto) {
    return this.tasksService.create(dto);
  }
}

Add PostgreSQL next

1. Install `@nestjs/typeorm typeorm pg`.
2. Replace the in-memory array with a `Task` entity and repository.
3. Keep DTOs, they still guard the HTTP boundary.

Checklist before production

• Environment-based config (`@nestjs/config`)
• Auth guard on mutating routes
• Structured logging and health check at `GET /health`

You now have the NestJS skeleton Kabim uses on client backend projects.