ObjectMakr

An abstract factory for dynamic attribute-based classes.

Usage

ObjectMakr lazily creates classes based on inheritance trees with additional properties. You can then make new instances of those classes at runtime.

The system works almost identically to traditional classes that extend each other, with the added benefit of lazy instantiation from plain old JavaScript objects.

Constructor

import { ObjectMakr } from "objectmakr";

const objectMaker = new ObjectMakr({
    inheritance: {
        Solid: {
            Block: {},
        },
    },
    properties: {
        Block: {
            photo: "Question Mark",
        },
        Solid: {
            size: 8,
        },
    },
});

const block = objectMaker.make("Block");

block.photo; // "Question Mark"
block.size; // 8

inheritance

A tree representing class inheritances, where keys are class names. The sub-objects under each class name key are classes inheriting from that class.

The root object is always Object, as with normal JavaScript classes.

properties

Flat mapping of class names to any properties added to that class' prototype.

indexMap

How properties can be mapped from an array to indices on created members. If this is passed in, class properties will be allowed to be specified as arrays.

const objectMaker = new ObjectMakr({
    indexMap: ["photo", "contents"],
    inheritance: {
        Solid: {
            Block: ["Question Mark", "Coin"],
            Brick: ["Bricks"],
        },
    },
    properties: {
        Block: ["Question Mark"],
        Solid: {
            size: 8,
        },
    },
});

const block = objectMaker.make("Block");

block.photo; // "Question Mark"
block.contents; // "Coin"

const brick = objectMaker.make("Brick");

brick.photo; // "Bricks"
brick.contents; // undefined

onMake

Member name for a function on instances to be called upon creation. If this is provided, any class instance with a member under this name will call that member as a function when made with make.

The function is called with the member as its scope, and takes in the member and the class name.

const calledOnMake = console.log.bind(console, "Creating:");
const objectMaker = new ObjectMakr({
    inheritance: {
        Solid: {
            Block: {},
        },
    },
    onMake: "creator",
    properties: {
        Solid: {
            creator: calledOnMake,
        },
    },
});

// Creating: class_1 {} Block
objectMaker.make("Block");

make

Creates a new instance of a class. If the class doesn't yet exist in-memory, it's created based on its inheritance and properties.

const block = objectMaker.make("Block");

block.photo; // "Question Mark"
block.size; // 8

make also accepts an additional settings parameter with any settings overrides to be shallow-copied onto the object.

const bigBlock = objectMaker.make("Block", {
    size: 16,
});

block.photo; // "Question Mark"
bigBlock.size; // 16

Development

This repository is a portion of the EightBittr monorepo. See its docs/Development.md for details on how to get started. 💖

Running Tests

yarn run test

Tests are written in Mocha and Chai. Their files are written using alongside source files under src/ and named *.test.ts?. Whenever you add, remove, or rename a *.test.t* file under src/, watch will re-run yarn run test:setup to regenerate the list of static test files in test/index.html. You can open that file in a browser to debug through the tests, or run yarn test:run to run them in headless Chrome.