@dmitriyzverev/pod

Simple implementation of Service Locator pattern with singletons and lazy loading

Intro

There are two main entities: pod and seed. Pod is a container for seeds. Seed is a function that get pod as an argument and returns some value. Seed can use any other seed from pod as a dependency. It is a way to organize your code into small pieces, that can be easily tested and reused.

Usage

1. Install dependencies:

   npm i -SE @dmitriyzverev/pod

2. Create pod and define your seeds inside:

   import {createPod} from '@dmitriyzverev/pod';
   const pod = createPod({
       seeds: {
           get user() {
               return {
                   name: 'Bob',
               };
           },
           get helloMessage() {
               return `Hello, ${pod.user.name}!`; // use "user" seed as a dependency
           },
       },
   });

   Now you can use any seed defined in pod:

   console.log(pod.helloMessage); // Hello, Bob!

Advanced usage

Singletons

By default, each seed is a singleton. It will be created only once, and only if requested. If you need to create a new seed instance for each seed request, disable the seed singleton in the singletons property:

import {createPod} from '@dmitriyzverev/pod';
const pod = createPod({
    seeds: {
        get user() {
            return {
                name: 'Bob',
            };
        },
    },
    singletons: {
        user: false, // disable singleton for "user" seed
    },
});
console.log(pod.user === pod.user); // false - each request creates a new instance

Exclude and include seeds

If you need to exclude some seeds from pod, use exclude property:

import {createPod} from '@dmitriyzverev/pod';
const pod = createPod({
    seeds: {
        get foo() {
            return 'foo';
        },
        get bar() {
            return 'bar';
        },
        get baz() {
            return 'baz';
        },
    },
});
const podWithoutFoo = pod.exclude('foo');
console.log(podWithoutFoo.foo); // undefined

Or you can include only some seeds:

const podWithFooAndBar = pod.include('foo', 'bar');
console.log(podWithFooAndBar.foo); // 'foo'
console.log(podWithFooAndBar.baz); // undefined

Both exclude and include methods create a new pod instance, so you can use them and don't worry about the original pod:

console.log(pod.foo); // 'foo' - still available in the original pod