METAMORPHOSIS-JS

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

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

QUICK START

INSTALL

npm install --save @fabio.formosa/metamorphosis

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';

@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;
  }

}

CREATE CONVERTER INSTANCE

const carToCarDtoConverter = new CarToCarDtoConverter();

Since they are decorated with @Converter, converters register theyself in a conversion registry.

USE CONVERSION HELPER

import { ConversionHelper } from '@fabio.formosa/metamorphosis'
...
ConversionHelper conversionHelper = new ConversionHelper();
const carDto = <CarDto> await conversionHelper.convert(car, CarDto);

if source hasn't Car as constructor name, you can specify the source type, so:

const carDto = <CarDto> await conversionHelper.convertBySource(car, Car, 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 conversionHelper.convert(planetDto, Planet);

DEBUG MODE

Debug mode shows log in console by default:

import { ConversionHelper } from '@fabio.formosa/metamorphosis'
...
ConversionHelper conversionHelper = new ConversionHelper({logger: true});

or you can pass a custom log function:

import { ConversionHelper } from '@fabio.formosa/metamorphosis'
...
ConversionHelper conversionHelper = new ConversionHelper({logger: msg => console.log(msg) });

REQUIREMENTS

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

CREDITS

Chameleon in this README file is a picture of ph. Egor Kamelev (pexels.com)