@buddh4/mapped-types v1.2.1

Description

This library provides mapped types for creating dynamic model classes and class-validator validation schemas with the help of following classes:

• PartialType: Sets all validation schema fields of a given type to @IsOptional
• IntersectionType: Combines two classes and their validation schema
• OmitType: Omits certain fields and validations from an existing class
• PickType: Picks certain fields with validation schema from an existing class

This library is heavily based on the implementation of the @nestjs/swagger module but contains some modifications as:

• Removed all nestjs dependencies and nestjs/swagger related metadata code
• Use of real inheritance in PartialType and IntersectionType, as opposed to property only inheritance
• Pass constructor arguments to inherited constructor

Note: In browser environments the inheritance of @Exclude and @Expose decorators for Pick-, Omit-, and the second class provided to IntersectionType does not work due to the following limitation of the class-transformer library issue.

Usage

The provided type helper classes can be used to create subclasses with altered validation schemas, without the need of redefining all properties of a class.

PartialType

With the PartialType helper, we can create a subclass which automatically adds an @IsOptional decorator to all properties of the base class.

import { IsString } from 'class-validator';
import { PartialType } from '@buddh4/mapped-types';

class CreateArticleDto {
  @IsString()
  title: string;

  @IsString()
  text;
}

class UpdateArticelDto extends PartialType(CreateDto) {}

Notes:

• Only properties which do have a validation rule in the base class will be attached with an @IsOptional rule.
• The created subclass will inherit all functions, this behavior differs from the original nestjs/swagger implementation.

OmitType

With the OmitType you can create a subclass which omits all selected fields and their validations.

import { IsString } from 'class-validator';
import { OmitType } from '@buddh4/mapped-types';

class UserDto {
  @IsString()
  username: string;

  @IsString()
  password;
}

class UserInfoDto extends OmitType(UserDto, ['password']) {}

Notes:

• The OmitType does not inherit any class functions, only properties.

PickType

The PickType behaves similar to the OmitType but instead of excluding certain fields it only includes the selected fields.

import { IsString } from 'class-validator';
import { PickType } from '@buddh4/mapped-types';

class UserDto {
  @IsString()
  username: string;

  @IsString()
  password;
}

class UserInfoDto extends PickType(UserDto, ['username']) {}

Notes:

• The PickType does not inherit any class functions, only properties.

IntersectionType

The IntersectionType can be used to merge the properties and their validation schema into a single subclass.

import { IsString } from 'class-validator';
import { IntersectionType } from '@buddh4/mapped-types';

class UserDto {
  @IsString()
  username: string;
}

class UserInfoDto {
  @Length(15)
  username: string;
}

class UserFormDto extends InterSectionType(UserDto, UserInfoDto) {}

Note:

• The IntersectionType will only inherit functions and the constructor from the first provided class but not the second one. So only the fields and validation schema of the second class will be merged into the resulting class.
• If one class of an IntersectionType sets an @Exclude on a field, the other class is not able to overwrite it with an @Expose.

Additional Notes

Class level Exclude and Expose are ignored

You need to manually set @Expose or @Exclude on the newly created types if required.