NestJS

[houstonTaleubou]

How to use DTOs (Data Transfer Objects) in NestJS?

[TatyOko28]

A DTO (Data Transfer Object) is a TypeScript class used to validate and transform incoming data. NestJS uses class-validatorand class-transformerfor validation.

Example of a DTO to create a user :

import { IsString, IsEmail, Length } from 'class-validator';

export class CreateUserDto {
  @IsString()
  @Length(3, 20)
  username: string;

  @IsEmail()
  email: string;
}

It is used in the controller with @Body():

import { Controller, Post, Body } from '@nestjs/common';
import { CreateUserDto } from './dto/create-user.dto';

@Controller('users')
export class UsersController {
  @Post()
  create(@Body() createUserDto: CreateUserDto) {
    return `User ${createUserDto.username} with email ${createUserDto.email} created!`;
  }
}

If the data does not follow the DTO rules, NestJS will automatically return a 400 Bad Request error .