Nestjs Entity param converter. Convert request parameter to domain entity

README.md

Nestjs Entity param converter pipe

Convert input param into domain entity.

@Controller('books')
export class BooksController {
  @Get('/:id')
  async getBook(@Param('id', IdToEntityPipe()) book: BookEntity): Promise<BookEntity> {
    return book;
  }
}

Inspired by:

• Java Spring Data Domain class converter
• PHP Symfony param converter

books-controller.ts

import { Controller, Get, Param } from '@nestjs/common';
import { IdToEntityPipe } from 'id-to-entity.pipe';

type BookEntity = {
  id: number;
  name: string;
};

@Controller('books')
export class BooksController {
  @Get('/:id')
  async getBook(@Param('id', IdToEntityPipe()) book: BookEntity): Promise<BookEntity> {
    return book;
  }
}

id-to-entity.pipe.ts

import { ArgumentMetadata, Injectable, Logger, NotFoundException, PipeTransform } from '@nestjs/common';
import { InjectEntityManager } from '@nestjs/typeorm';
import { EntityManager } from 'typeorm';

export const IdToEntityPipe = (property: string = 'id') => {
  @Injectable()
  class IdToEntityPipe implements PipeTransform {
    readonly logger = new Logger(IdToEntityPipe.name);

    constructor(@InjectEntityManager() readonly entityManager: EntityManager) {}

    async transform(value: string, metadata: ArgumentMetadata): Promise<any> {
      const { metatype } = metadata;

      const entity = await this.entityManager.findOne(metatype, {
        where: { [property]: value },
      });
      if (!entity) {
        this.logger.log(`Entity not found: ${metatype} with ${property}:${value}`);
        throw new NotFoundException(`${metatype} with ${property}:${value} not found`);
      }

      this.logger.log(`Entity found ${metatype} with ${property}:${value} -> ${entity}`);
      return entity;
    }
  }

  return IdToEntityPipe;
};