codinronan / needlepoint

ES6 and beyond dependency injection framework.

Needlepoint

Needlepoint is a dependency injection framework for Node.js and other Javascript environments where ES6 is supported.

Needlepoint is licensed under the MIT license.

Note: This library is very early in development and was largely developed as an exercise, though I intend to use Needlepoint in my own future projects.

Requirements

Needlepoint requires a Javascript environment such as Node.js. Though the library is designed to use new features such as ES6 classes and the proposed ES7 decorators, Babel is included as a dependency to make the library compatible with environments that do not support these features directly.

Getting Started

To use Needlepoint, install it with npm:

npm install --save needlepoint

If you're not using a Javascript environment that supports both ES6 classes and ES7-style decorators (e.g. Node.JS), then you must configure Babel. This can be done pretty easily.

Babel 5

If you are using Babel 5.x, you can simply add ES7 decorators to the opt-in features:

require('babel/register')({
    optional: ['es7.decorators']
});

Babel 6

Because Babel 6 has not entirely implemented ES7 decorators, you must install another NPM package to enable the legacy ES7 decorators (as well as the corresponding presets, which I've included a sample of) and then configure Babel as follows:

npm install --save babel-plugin-transform-decorators-legacy

require('babel/register')({
    presets: ['es2015', 'stage-0', 'stage-1'],
    plugins: ['babel-plugin-transform-decorators-legacy']
});

After this, you can simply import the container where ever your application needs to inject dependencies:

import {container} from 'needlepoint';

From there, you can resolve dependencies:

import {container} from 'needlepoint';
import {MyDependency} from './my-dependency';

var instanceOfDependency = container.resolve(MyDependency);
instanceOfDependency.performMethod();

You can also declare dependencies of your classes with the @dependencies() decorator:

import {container, dependencies} from 'needlepoint';
import {MyDependency} from './my-dependency';

@dependencies(MyDependency)
class HasDependencies {
    constructor(myDependency) {
        this.myDependency = myDependency;
    }
}

var instance = container.resolve(HasDependencies);
instance.myDependency.performMethod();

Dependencies of a class are injected through the constructor. The objects passed into the constructor are instances of the requested dependencies.

Or, if you want a class to be a singleton (i.e. only one instance of the class will be created for your entire application):

import {container, singleton} from 'needlepoint';

@singleton
class SingletonDependency {
    constructor() {

    }
}

If a class is declared to be a @singleton, then one instance will be created the first time the class is listed as a dependency or resolved, and this instance will be cached and used when other classes need an instance of it.