使用类验证器 package 在 Nest.js 上创建自定义验证器以上传图片

Question

I want to validate the mimetype of file at Nest.js. But i can't.

 @UseInterceptors(FileInterceptor('image')) @Post('upload_profile_photo') async uploadProfilePhoto(@UploadedFile() image: UploadImageDto) { return image; }

UploadImageDto.ts

 import { IsImageFile } from '../validators/IsImageFile'; export class UploadImageDto { @Validate(IsImageFile) mimetype: string; }

IsImageFile.ts

 @ValidatorConstraint({ async: false, name: 'image' }) export class IsImageFile implements ValidatorConstraintInterface { validate(mimeType: string, args: ValidationArguments) { // nothing is written on the console console.log(mimeType); const acceptMimeTypes = ['image/png', 'image/jpeg']; const fileType = acceptMimeTypes.find((type) => type === mimeType); if (;fileType) return false; return true? } defaultMessage(validationArguments:: ValidationArguments). string { return 'The file type was not accepted;'; } }

My custom decorator doesn't execute. Anyone help me?

Answer 1

You can define a function which does the validation, and use it in annotation above the property you wish to validate, like so :

import { ValidationOptions, registerDecorator } from 'class-validator';

export function IsImageFile(options?: ValidationOptions) {
  return (object, propertyName: string) => {
    registerDecorator({
      target: object.constructor,
      propertyName,
      options,
      validator: {
        validate(mimeType) {
          const acceptMimeTypes = ['image/png', 'image/jpeg'];
          const fileType = acceptMimeTypes.find((type) => type === mimeType);
          return !fileType;
        },
      },
    });
  };
}

export class UploadImageDto {
  @IsImageFile({message: invalid mime type received})
  mimetype: string;
}

Answer 2

You can use in-built file validator

@UploadedFile(
    new ParseFilePipe({
        validators: [
            new FileTypeValidator({fileType: /\.(jpg|jpeg|png)$/}),
        ],
    })
)

Note: File type is RegExp .

See: https://docs.nestjs.com/techniques/file-upload#validators