README.md

Specosaur

Specification pattern library for Deno inspired by Eric Evans's book about DDD.

Portage for Deno of spoeck npm module

Here is an article from Martin Fowler website about this pattern;

Types documenation :

Typescript documentation here

Create a specification :

import { defineSpecification } from 'https://deno.land/x/specosaur/mod.ts';

type Denosaur = {
  color: string;
  dietPlan: 'carnivore' | 'vegetarian' | 'omnivorous';
  weigth: number;
  size: number;
};

const denosaur: Denosaur = {
  color: 'green',
  dietPlan: 'carnivore',
  weigth: 1000,
  size: 10,
};

const denosaurIsBlue = defineSpecification({
  name: 'denosaurIsBlue',
  desc: 'Denosaur is blue',
  isSatisfiedBy: (denosaur: Denosaur) => denosaur.color === 'blue',
});

const result = denosaurIsBlue.isSatisfiedBy(denosaur);

console.log(result.value); // => false

Result format :

The specification isSatisifiedBy function will always return an object with these properties.

• name: Is the name of the specification.
• desc: Is the description of the specification.
• value: Is the boolean that indicate if the specification is respected.
• details: Is the list of all sub specifications results.

// With a simple rule :
const result = {
  name: 'denosaurIsBlue',
  desc: 'Denosaur is blue',
  value: false,
  details: [{ name: 'denosaurIsBlue', value: false, desc: 'Denosaur is blue' }],
};

// With a composite rule :
const isBlueAndCarnivore = denosaurIsBlue.and(
  denosaurIsCarnivore,
  'isBlueAndCarnivore',
);

const compositeRuleResult = {
  name: 'isBlueAndCarnivore',
  desc: 'Denosaur is blue AND (Denosaur is carnivore)',
  value: true,
  details: [
    { name: 'denosaurIsBlue', value: true, desc: 'Denosaur is blue' },
    { name: 'denosaurIsCarnivore', value: true, desc: 'Denosaur is carnivore' },
  ],
};

Combining specifications with operator :

AND operator:

const isBlueAndCarnivore = denosaurIsBlue.and(
  denosaurIsCarnivore,
  'isBlueAndCarnivore',
);

OR operator :

const isBlueOrCarnivore = denosaurIsBlue.or(
  denosaurIsCarnivore,
  'isBlueOrCarnivore',
);

XOR operator :

const isBlueXorCarnivore = denosaurIsBlue.xor(
  denosaurIsCarnivore,
  'isBlueXorCarnivore',
);

NOT operator :

const isBlueAndNotCarnivore = denosaurIsBlue.and(
  denosaurIsCarnivore.not(isNotCarinvore),
  'isBlueAndNotCarnivore',
);