How to reuse mutler settings to specify a different folder for a route

Question

I initialize MutlerModule to app.module:

MulterModule.registerAsync({
    imports: [ ConfigModule ],
    inject: [ ConfigService ],

    async useFactory(configService: ConfigService)
    {
        const uploadFolder = configService.get<IConfig[ "uploadFolder" ]>("uploadFolder");

        return {
            storage: diskStorage({
                destination: uploadFolder,
                filename(req, file, cb)
                {
                    const filename = `${ Date.now() }-${ file.originalname }`;

                    cb(null, filename);
                }
            })
        };
    }
}),

In uploadFolder we have uploads. Further for some route I want to save not in uploads but in uploads/category, how can I do it without duplicating the code?

What I need to change somewhere that the files that are sent to this route go to uploads/category

@Controller("category")
export class CategoryController
{
    @UseInterceptors(FileInterceptor("image"))
    @Post()
    async create(
        @UploadedFile(
            new ParseFilePipeBuilder()
                .addFileTypeValidator({ fileType: ALLOWED_IMAGE_TYPES.join() })
                .addMaxSizeValidator({ maxSize: MAX_FILE_SIZE_BYTES })
                .build({
                    fileIsRequired: false,
                    errorHttpStatusCode: HttpStatus.UNPROCESSABLE_ENTITY
                })
        )
        image
    )
    {
        console.log(image);
    }
}

Answer 1

Path Based Folder

You can decide which folder to upload by passing a function to destination parameter :

MulterModule.registerAsync({
  imports: [ConfigModule],
  inject: [ConfigService],
  async useFactory(configService: ConfigService) {
    const baseUploadFolder = configService.get<string>('uploadFolder'); // Base folder from config

    return {
      storage: diskStorage({
        destination: (req, file, cb) => {
          // Add logic to determine folder dynamically
          const folder = req.path === "food" ? 'category/food' : 'default';
          const uploadFolder = `${baseUploadFolder}/${folder}`;
          
          // Ensure folder exists
          import('fs').then(fs => {
            if (!fs.existsSync(uploadFolder)) {
              fs.mkdirSync(uploadFolder, { recursive: true });
            }
          });

          cb(null, uploadFolder);
        },
        filename: (req, file, cb) => {
          const filename = `${Date.now()}-${file.originalname}`;
          cb(null, filename);
        },
      }),
    };
  },
});

Using this you can apply check where to store files based upon the path you get request from user.

Re-usable Multer Config way

And if you want to handle this at controller level you can create a function to get multer configuration :

import { diskStorage } from 'multer';
import * as path from 'path';

export function createMulterConfig(folder: string) {
  return {
    storage: diskStorage({
      destination: path.join(__dirname, '..', '..', 'upload', folder),
      filename: (req, file, cb) => {
        const filename = `${Date.now()}-${file.originalname}`;
        cb(null, filename);
      },
    }),
  };
}

In your controller, pass the specific folder name to the factory function and use it with FileInterceptor.

import { Controller, Post, UploadedFile, UseInterceptors } from '@nestjs/common';
import { FileInterceptor } from '@nestjs/platform-express';
import { createMulterConfig } from './multer-config.factory';

@Controller('category')
export class CategoryController {
  @Post('default')
  @UseInterceptors(FileInterceptor('file', createMulterConfig('default')))
  uploadDefault(@UploadedFile() file: Express.Multer.File) {
    return { message: 'File uploaded to default folder', file };
  }

  @Post('category')
  @UseInterceptors(FileInterceptor('file', createMulterConfig('category')))
  uploadCategory(@UploadedFile() file: Express.Multer.File) {
    return { message: 'File uploaded to category folder', file };
  }
}