How to construct DTO in Nest.js for @Body

Question

I am a beginner in Nest.js and I found it extremely good. I read the official docs and learned about DTOs. When My Body is like this:

then I can simply create user.dto.ts like this:

import { IsNotEmpty } from 'class-validator';

export class UserDTO {
  @IsNotEmpty()
  username: string;
  @IsNotEmpty()
  password: string;
}

Then I use this in my controller like this.

  @Post('login')
  @UsePipes(new ValidationPipe())
  login(@Body() data: UserDTO) {
    return this.userService.login(data);
  }

But my question is what if my Body is something like this.

{
  "data": {
    "username": "username",
    "password": "password",
  }
}

then what modifications I need to make in my ```user.dto.ts`` file to make it work? Thanks

Answer 1

The answer is: You don't need to modify your DTO.

@Body() decorator also takes in an optional argument: @Body(path?: string).

The key here is to understand what @Body() does. @Body() without any argument will return req.body object. @Body('path') will return req.body.path (or req.body['path']. With this knowledge, you can pass 'data' in @Body('data') and it will return req.body.data which will be your DTO.

@Post('login')
@UsePipes(new ValidationPipe())
login(@Body('data') data: UserDTO) {
   // data will be your req.body.data which is your UserDTO
   return this.userService.login(data);
}