generic based rosie constructor

index.ts

import { Factory } from 'rosie';
import { NonFunctionKeys } from 'utility-types';

// maybe typeorm entity
class Entity {
  constructor() {
    this.a = 0;
    this.b = null;
  }
  public a: number;
  public b: Date | null;
  public f() { return 1; }
}

function create_simple(
  ...params: Partial<Entity>[]
): Entity {
  const {
    a,
    b,
  } = params[0];
  const ent = new Entity();
  ent.a = a!;
  ent.b = b!;
  return ent;
}

function generate<T extends object>(ctor: new () => T) {
  return (...params: Partial<T>[]) => {
    const skel = params[0];
    const keys = Object.keys(skel) as NonFunctionKeys<T>[];

    const ent = new ctor();
    for (const key of keys) {
      if (skel[key] !== undefined) {
        ent[key] = skel[key]!;
      }
    }
    return ent;
  };
}

Factory.define<Entity>('data_simple', create_simple)
  .attr('a', () => 1)
  .attr('b', () => null);

Factory.define<Entity>('data_generic', generate(Entity))
  .attr('a', () => 2)
  .attr('b', () => null);

function main() {
  const x = Factory.build<Entity>('data_simple', { a: 12, b: new Date() });
  console.log(x);

  const y = Factory.build<Entity>('data_generic', { a: 123, b: new Date() });
  console.log(y);
}
main();