title: nestjs+ swagger file upload with other dto
body: <p>I have a difficult part while using nestjs and swagger, so I ask a question.</p>
  <pre class="lang-js prettyprint-override"><code>@Post('import')
    @ApiConsumes('multipart/form-data')
    @UseInterceptors(
      FileFieldsInterceptor(
        [
          { name: 'file', maxCount: 5 },
        ],
        {
          storage: multerS3({
            s3: s3,
            bucket: process.env.AWS_S3_BUCKET_NAME,
            acl: 'public-read',
            key: function (request, file, cb) {
              cb(
                null,
                `test/${file.fieldname}/${uuid()}_${file.originalname
                }`,
              );
            },
          }),
          fileFilter: extensionHelper,
        },
      ),
    )
    async upload(
      @Body() dto: AddDto,
      @UploadedFiles() file?: Express.MulterS3.File[],
    ): Promise&lt;void&gt; {
      
    }
  </code></pre>
  <pre class="lang-js prettyprint-override"><code>export class AddDto {
    @IsString()
    @IsOptional()
    firstName?: string;
  
    @IsString()
    @IsOptional()
    lastName: string;
  
    @IsOptional()
    @ValidateNested({ each: true })
    @Type(() =&gt; AdditionalDto)
    addData: AdditionalDto[];
  }
  </code></pre>
  <pre class="lang-js prettyprint-override"><code>export class AdditionalDto {
  
    @IsString()
    title: string;
  
    @IsString()
    sellYn: string;
  
    @IsEnum(Language)
    language: Language;
  
    @IsString()
    description: string;
  }
  </code></pre>
  <p>My code is written as above.
  When sending a file and an array of AddDto through swagger, AddDto is in json format.</p>
  <p>When received through swagger, if dto.addData is output,</p>
  <pre class="lang-json prettyprint-override"><code>[{&quot;title&quot;:&quot;aa&quot;, &quot;sellYn&quot;:&quot;Y&quot;, &quot;language&quot;:&quot;en&quot;, &quot;description&quot;:&quot;description&quot;},{&quot;title &quot;:&quot;bb&quot;, &quot;sellYn&quot;:&quot;Y&quot;, &quot;language&quot;:&quot;kr&quot;, &quot;description&quot;:&quot;description&quot;}]
  </code></pre>
  <p>but, cannot used like dto.addData[0] and dto.addData[0].title .
  How can I use dto in non-json format?</p>
  <p>I want to know how to process file upload and dto in one time,
  instead of sending them separately.
  thank you!</p>