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File Uploads

Bun parses multipart/form-data natively, so uploaded files arrive as standard Web File objects on the request body. There’s no multer, and the FileInterceptor/@UploadedFile decorators from @nestjs/platform-express don’t apply here — use the patterns below instead.

Via `@Body()`

The simplest path: the parsed multipart body exposes files and scalar fields together.

import { Body, Controller, Post } from '@nestjs/common';

@Controller('upload')
export class UploadController {
  @Post('avatar')
  async avatar(@Body() body: { file: File; userId: string }) {
    const bytes = await body.file.arrayBuffer();
    await Bun.write(`./uploads/${body.userId}`, bytes);
    return { name: body.file.name, size: body.file.size, type: body.file.type };
  }
}

Via `@UploadedFile()` / `@UploadedFiles()`

For ergonomics close to platform-express, the package ships Bun-native param decorators that pull files straight out of the parsed body.

import { Controller, Post } from '@nestjs/common';
import { UploadedFile, UploadedFiles } from 'nestjs-platform-elysia';

@Controller('upload')
export class UploadController {
  @Post('single')
  single(@UploadedFile('file') file: File) {
    return { name: file.name, size: file.size };
  }

  @Post('gallery')
  gallery(@UploadedFiles('photos') photos: File[]) {
    return { count: photos.length };
  }
}

@UploadedFile(field) returns the File for that field (or undefined).
@UploadedFiles(field) returns an array — repeated form fields (photos, photos, …) are collected automatically.
Called with no argument, @UploadedFile() returns the first file in the body and @UploadedFiles() returns every file across all fields.

Validation with `@RouteSchema`

Pair uploads with Elysia’s t.File() for framework-level validation (size, MIME type) before your handler runs:

import { Post } from '@nestjs/common';
import { RouteSchema } from 'nestjs-platform-elysia';
import { t } from 'elysia';

@Post('document')
@RouteSchema({
  body: t.Object({
    file: t.File({ type: 'application/pdf', maxSize: '5m' }),
  }),
})
upload(@UploadedFile('file') file: File) {
  return { name: file.name };
}