db-class-validator

db-class-validator is a npm package for validating request parameters from database in nestjs using class-validator and typeorm

Table of Contents

• Installation
• Usage
• Features
  • Exists
  • IsUnique
• Explanation

Installation

To install it, using npm:

npm install db-class-validator

Usage

1. To use this you first have to add following line in your main.ts file.

 useContainer(app.select(AppModule), { fallbackOnErrors: true });

useContainer is imported from class-validator it is used so that the validation function uses AppModule as the root module for dependency resolution.

2. Add ExistsValidation class in your AppModule providers

import { Module } from '@nestjs/common';
import { ExistsValidation } from 'db-class-validator'; // Importing Validator Class

@Module({
  imports: [],
  controllers: [],
  providers: [
    ExistsValidation,  // Add This Here
  ],
})
export class AppModule { }

3. Use the decorator on the property you want to validate in the Dto

import { Exists } from 'db-class-validator'; // Importing Decorator

export class YourDto { 
   @Exists(existsOptions,ValidatorOptions)  // Using Decorator
   property: string;
}

Features

The library has following decorators to validate your request data:

Exists

This decorator checks if the field under validation exists in the database and will throw error if it is not.

import { Exists } from 'db-class-validator'; // Importing Decorator

export class YourDto { 
  @Exists(
      {
          tableName: 'TABLE_NAME_IN_DATABASE',
          columnName?: 'COLUMN_NAME_IN_DATABASE'   // Column name is optional if it is not provided it will consider property name as column name
      },
      ValidatorOptions?
  )  // Using Decorator
  property: string;
}

This valdiation decorator uses ExistsValdiation Class for validation, which need to be imported in AppModule

import { Module } from '@nestjs/common';
import { ExistsValidation } from 'db-class-validator'; // Importing Validator Class

@Module({
 imports: [],
 controllers: [],
 providers: [
   ExistsValidation,  // Add This Here
 ],
})
export class AppModule { }

IsUnique

This decorator checks if the field under validation is unique and do not exists in the database.

import { IsUnique } from 'db-class-validator'; // Importing Decorator

export class YourDto { 
  @IsUnique(
      {
          tableName: 'TABLE_NAME_IN_DATABASE',
          columnName?: 'COLUMN_NAME_IN_DATABASE'   // Column name is optional if it is not provided it will consider property name as column name
      },
      ValidatorOptions?
  )  // Using Decorator
  property: string;
}

It can also be used to check if field under validation is unique but not against certain row, which is useful when validating during update operations

export class YourDto { 
  @IsUnique(
      {
          tableName: 'TABLE_NAME_IN_DATABASE',
          columnName?: 'COLUMN_NAME_IN_DATABASE',   // Column name is optional if it is not provided it will consider property name as column name
          valueToBeIgnored: VALUE_TO_BE_IGNORED, // It takes string | number | (ValidationArguments) => string | number
          valueToBeIgnoredColumn: 'COLUMN_NAME_TO_BE_IGNORED_IN_DATABASE'  // If `valueToBeIgnoredColumn` is not provided it checks in `id` column
      },
      ValidatorOptions?
  )  // Using Decorator
  property: string;
}

This valdiation decorator uses IsUniqueValdiation Class for validation, which need to be imported in AppModule

import { Module } from '@nestjs/common';
import { IsUniqueValidation } from 'db-class-validator'; // Importing Validator Class

@Module({
 imports: [],
 controllers: [],
 providers: [
   IsUniqueValidation,  // Add This Here
 ],
})
export class AppModule { }

Explanation

The package uses typeorm dataSource and queryRunner to check if value exists in the database or not

  const queryRunner = this.dataSource.createQueryRunner();
  const result = await queryRunner.query(query);

  queryRunner.release();