CRUD operations in NestJS

Introduction

CRUD operations let you create, read, update, and delete data in your app. They are the basic actions to manage information.

Building a user management system where you add, view, edit, or remove users.

Creating a blog where you write, read, update, or delete posts.

Managing products in an online store with add, list, update, and delete features.

Syntax

NestJS

import { Controller, Get, Post, Put, Delete, Body, Param } from '@nestjs/common';

@Controller('items')
export class ItemsController {
  @Get()
  findAll() {}

  @Get(':id')
  findOne(@Param('id') id: string) {}

  @Post()
  create(@Body() createItemDto) {}

  @Put(':id')
  update(@Param('id') id: string, @Body() updateItemDto) {}

  @Delete(':id')
  remove(@Param('id') id: string) {}
}

Use decorators like @Get, @Post, @Put, and @Delete to define HTTP methods.

@Param gets data from the URL, @Body gets data from the request body.

Examples

Gets all items when you visit /items with a GET request.

NestJS

@Get()
findAll() {
  return 'Return all items';
}

Creates a new item using data sent in the request body.

NestJS

@Post()
create(@Body() createItemDto) {
  return `Create item with name: ${createItemDto.name}`;
}

Updates an existing item by its ID with new data.

NestJS

@Put(':id')
update(@Param('id') id: string, @Body() updateItemDto) {
  return `Update item ${id} with name: ${updateItemDto.name}`;
}

Deletes an item by its ID.

NestJS

@Delete(':id')
remove(@Param('id') id: string) {
  return `Delete item with id ${id}`;
}

Sample Program

This controller manages a list of items in memory. You can add, get, update, and delete items by their ID.

NestJS

import { Controller, Get, Post, Put, Delete, Body, Param } from '@nestjs/common';

interface Item {
  id: number;
  name: string;
}

@Controller('items')
export class ItemsController {
  private items: Item[] = [];
  private idCounter = 1;

  @Get()
  findAll(): Item[] {
    return this.items;
  }

  @Get(':id')
  findOne(@Param('id') id: string): Item | string {
    const item = this.items.find(i => i.id === +id);
    return item || 'Item not found';
  }

  @Post()
  create(@Body() createItemDto: { name: string }): Item {
    const newItem = { id: this.idCounter++, name: createItemDto.name };
    this.items.push(newItem);
    return newItem;
  }

  @Put(':id')
  update(@Param('id') id: string, @Body() updateItemDto: { name: string }): Item | string {
    const item = this.items.find(i => i.id === +id);
    if (!item) return 'Item not found';
    item.name = updateItemDto.name;
    return item;
  }

  @Delete(':id')
  remove(@Param('id') id: string): string {
    const index = this.items.findIndex(i => i.id === +id);
    if (index === -1) return 'Item not found';
    this.items.splice(index, 1);
    return `Deleted item with id ${id}`;
  }
}

Important Notes

In real apps, data usually comes from a database, not memory.

Use DTOs (Data Transfer Objects) to validate and type-check data.

Each HTTP method matches a CRUD action: GET=read, POST=create, PUT=update, DELETE=delete.

Summary

CRUD operations let you manage data by creating, reading, updating, and deleting.

In NestJS, use controllers with decorators like @Get, @Post, @Put, and @Delete.

Use @Param to get URL data and @Body to get data sent by the client.