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:

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

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);
}

Answer 2

You may create a wrapper class that would carry your dto such as

export class Data<T> {

  @ApiModelProperty()
  readonly data: T;

  constructor(data: any = {}) {
    this.data = data;
  }
}

and in your controller you will have

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

in your service you will do something like

return new Data(this.userDto);