METAMORPHOSIS-NESTJS

"Nothing is lost, nothing is created, everything is transformed" _Lavoisier

Metamorphosis-NestJS is the NodeJS version of Metamorphosis, an utility library to ease conversions of objects, provided as java, javascript and NestJS as well.

Metamorphosis-NestJS has been adapted to the popular framework NestJS, so it exports a conversion service, that you can import and use into your application as hub of all convertions: for example, entities to DTOs and/or viceversa

QUICK START

INSTALL

npm install --save @fabio.formosa/metamorphosis-nest

IMPORT MODULE

import { MetamorphosisNestModule } from '@fabio.formosa/metamorphosis-nest';

@Module({
  imports: [MetamorphosisModule.register()],
  ...
}
export class MyApp{
}

NEW CONVERTER

Create a new converter class, implementing the interface Converter<Source, Target> and decorate the class with @Convert

import { Convert, Converter } from '@fabio.formosa/metamorphosis';

@Injectable()
@Convert(Car, CarDto)
export default class CarToCarDtoConverter implements Converter<Car, CarDto> {
  
  public convert(source: Car): CarDto {
    const target = new CarDto();
    target.color = source.color;
    target.model = source.model;
    target.manufacturerName = source.manufacturer.name;
    return target;
  }

}

In the above example, the converter is @Injectable(), so is a NestJs Service.

USE CONVERSION SERVICE

When your converters are instanciated by NestJs, they will be registered into the conversion service. The conversion service is the hub for all conversions. You can inject it and invoke the convert method.

import { ConversionService } from '@fabio.formosa/metamorphosis-nest';

@Injectable()
class CarService{

  constructor(private convertionService: ConvertionService){}

  public async getCar(id: string): CarDto{
      const car: Car = await CarModel.findById(id);
      return <CarDto> await this.convertionService.convert(car, CarDto);
  }

}

ADVANCED FEATURES

CONVERT ARRAYS

const cars: Car[] = ...
const carDtos = <CarDto[]>  await this.convertionService.convertAll(cars, CarDto);

ASYNC CONVERSIONS

If your converter must be async (eg. it must retrieve entities from DB):

@Injectable()
@Convert(PlanetDto, Planet)
export default class PlanetDtoToPlanet implements Converter<PlanetDto, Promise<Planet>> {
  
  async convert(source: PlanetDto): Promise<Planet> {
   ...
  }

}

• Define Planet as target type in @Convert
• declare Promise<Planet> in Converter interface.
• The convert method will be async.

When you invoke conversionService you must apply await if you know for that conversion is returned a Promise.

const planet = <Planet> await conversionService.convert(planetDto, Planet);

or in case of conversion of an array:

const planets = <Planet[]> await Promise.all(conversionService.convert(planetDto, Planet));

TYPEGOOSE SUPPORT

If you have to convert mongoose document into DTO, it's recommended to use Typegoose and class-transformer.

1. Add dependency:

   npm install --save @fabio.formosa/metamorphosis-typegoose-plugin

2. Register conversion service with metamorphosis-typegoose-plugin

   import { MetamorphosisNestModule } from '@fabio.formosa/metamorphosis-nest';
   import TypegoosePlugin from '@fabio.formosa/metamorphosis-typegoose-plugin/dist/typegoose-plugin';
   import { MetamorphosisPlugin } from '@fabio.formosa/metamorphosis';
   
   const typegoosePlugin = new TypegoosePlugin();
   
   @Module({
     imports: [MetamorphosisModule.register({logger: false, plugins: [typegoosePlugin])],
     ...
   }
   export class MyApp{
   }

3. Define the type of your model and the moongose schema using decorators (@prop). (note: team is annotate by @Type decorator provided by class-transformer in order to use plainToClass function)

   @modelOptions({
     existingMongoose: mongoose,
     collection: 'players'
   })
   class Player{
       _id: ObjectID;
   
       @prop({require : true})
       name: string;
          
       @prop()
       score: number;
          
       @Type(() => Team)
       @prop({require : true})
       team: Team;
   }
   
   class Team{
     _id: ObjectID;
        
     @prop({require : true})
     name: string;
        
     @prop({require : true})
     city: string;
   }
   

4. Define your DTOs

     class PlayerDto{
       id: string;
       name: string;
       team: string;
     }
   
     class TeamDto{
       id: string;
       name: string;
       city: string;
     }

5. Create converters

     import {Converter, Convert} from '@fabio.formosa/metamorphosis';
   
     @Convert(Player, PlayerDto)
     class PlayerConverterTest implements Converter<Player, PlayerDto> {
            
       public convert(source: Player): PlayerDto {
         const target = new PlayerDto();
         target.id = source._id.toString();
         target.name = source.name;
         target.team = source.team.name;
         return target;
       }
   
     }
   
     @Convert(Team, TeamDto)
     class TeamConverterTest implements Converter<Team, TeamDto> {
            
       public convert(source: Team): TeamDto {
         const target = new TeamDto();
         target.id = source._id.toString();
         target.name = source.name;
         target.city = source.city;
         return target;
       }
   
     }

6. Use ConversionService

     import {ConversionService} from '@fabio.formosa/metamorphosis-nest';
   
     @Injectable()
     class MyService{
   
       constructor(private readonly ConversionService conversionService){}
          
       doIt(){      
         const foundPlayerModel = await PlayerModel.findOne({'name': 'Baggio'}).exec() || player;
   
         const playerDto = <PlayerDto> await this.conversionService.convert(foundPlayerModel, PlayerDto);
   
         //if you want convert only the team (and not also the Player)
         const teamDto = <TeamDto> await conversionService.convert(foundPlayer.team, TeamDto);
       }

TYPEORM EXAMPLE

typeORM is supported by metamorphosis. Following an example (it doesn't show the converter because it's trivial, if you read above the doc):

 let product = new Product();
 product.name = 'smartphone';
 product.pieces = 50;

 const productRepository = connection.getRepository(Product);
 product = await productRepository.save(product);


 const productDto: ProductDto = <ProductDto> await conversionService.convert(product, ProductDto);

or if your entity extends BaseEntity

 let product = new Product();
 product.name = 'smartphone';
 product.pieces = 50;
 product = await product.save(product);


 const productDto: ProductDto = <ProductDto> await conversionService.convert(product, ProductDto);

In case of conversion from DTO to entity:

@Injectable()
@Convert(ProductDto, Product)
export default class ProductDtoConverterTest implements Converter<ProductDto, Promise<Product>> {

  constructor(private readonly connection: Connection){}

  public async convert(source: ProductDto): Promise<Product> {
    const productRepository: Repository<Product> = this.connection.getRepository(Product);
    const target: Product | undefined = await productRepository.findOne(source.id);
    if(!target)
      throw new Error(`not found any product by id ${source.id}`);
    target.name = source.name;
    return target;
  }

}

DEBUG MODE

To activate debug mode

import { MetamorphosisNestModule } from '@fabio.formosa/metamorphosis-nest';

@Module({
  imports: [MetamorphosisModule.register({logger: true})],
  ...
}
export class MyApp{
}

In this case, metamorphosis will send log to console. Otherwise, you can pass a custom debug function (msg: string) => void , e.g:

import { MetamorphosisNestModule } from '@fabio.formosa/metamorphosis-nest';

const myCustomLogger = {
  debug: (msg: string) => {
    winston.logger(msg); //example
  }
}

@Module({
  imports: [MetamorphosisModule.register({logger: myCustomLogger.debug})],
  ...
}
export class MyApp{
}

At the moment, MetamorphosisNestModule uses console to log. Soon, it will be possible to pass a custom logger.

REQUIREMENTS

• TypeScript 3.2+
• Node 8, 10+
• emitDecoratorMetadata and experimentalDecorators must be enabled in tsconfig.json

CREDITS

Red Chameleon in this README file is a picture of ph. George Lebada (pexels.com)