AppController.ts

@Controller()
export class AppController {
  @ApiBody({ type: BodyDto, description: 'desc' })
  @ApiConsumes('multipart/form-data')
  @UseInterceptors(FileInterceptor('fileUpload'), new FileRequestMapperInterceptor('fileUpload'))
  @Post()
  example(
	  @Body() body: BodyDto,
  ): BodyDto {
    console.log(body) // exists fileUpload
    return body;
  }
}

BodyDto.ts

class BodyDto {
	@ApiProperty({ default: 'asd' })
	public someField: string = 'asd';

	@ApiProperty({ type: 'string', format: 'binary' })
	public fileUpload: any;
}

FileRequestMapperInterceptor.ts

@Injectable()
export class FileRequestMapperInterceptor implements NestInterceptor {
    constructor(
        private fieldName: string,
    ) {
    }
    intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
        const req = context.switchToHttp().getRequest();
        req.body[this.fieldName] = req.file;

        return next.handle();
    }
}