Js IoC

Inverse of Control (IoC) Service Container for ES6.

Before you continue reading, you should know that this package is heavily inspired by Taylor Otwell's Service Container in Laravel. Please go read the documentation, to gain a better understanding of what a Service Container is and how they are intended to work... and please do support Laravel!

Limitations

Because this is JavaScript, you will not have the same capabilities as a PHP version of the IoC, due to the "poor" support of Reflections.

Contents

• How to install
• Import the IoC
• Bindings
  • Bind to a callback
  • Bind to an instance
  • Bind singletons
  • Aliases
• Resolving nested dependencies
• Delete Bindings
• Contribution
• Acknowledgement
• Versioning
• License

How to install

npm install @aedart/js-ioc

Import the IoC

The IoC is exported as a singleton instance, which means that you only have to import and then you can start using it straight away.

import IoC from '@aedart/js-ioc';

Bindings

The basic principle behind an IoC is that you "bind" a resource to the container. This allows you to resolve it (to fetch it) at some later point in your application.

In other words, think of a binding as a factory method.

Bind to a callback

Simple binding

import IoC from '@aedart/js-ioc';

// Your class
class Box {
    // ... implementation not shown .../
}

// Bind "my-box" to a callback
IoC.bind('my-box', () => {
    return new Box();
});

// Later in your application, you can resolve "my-box"
let box = IoC.make('my-box'); // Resolves to Box

Binding with arguments

import IoC from '@aedart/js-ioc';

// Your class
class Box {
    // ... implementation not shown .../
}

// Bind "my-box" to a callback
IoC.bind('my-box', (ioc, params) => {
    return new Box(params.width, params.height);
});

// Later in your application, you can resolve "my-box"
let box = IoC.make('my-box', {width:50, height:60}); // Resolves to Box

Bind to an instance

In this context, an instance is an object that can be "newed up" - e.g. a class that will be initialised.

// Bind instance
IoC.bindInstance('my-box', Box);

// Later... resolve "my-box" - will return "new Box"
let box = IoC.make('my-box');

Arguments

You can also pass in arguments for the constructor, via the make method.

// Bind instance
IoC.bindInstance('my-box', Box);

// Later... resolve "my-box" - will return "new Box"
let box = IoC.make('my-box', {width:50, height:60});

Bind singletons

Via callback

// Bind as a singleton
IoC.singleton('my-box', (ioc, params)=>{
    return new Box();
});

// Later in your application...
let boxA = IoC.make('my-box');
let boxB = IoC.make('my-box');

console.log(boxA === boxB); // true

Via instance

// Bind as a singleton
IoC.singletonInstance('my-box', Box);

// Later in your application...
let boxA = IoC.make('my-box');
let boxB = IoC.make('my-box');

console.log(boxA === boxB); // true

Set instance directly

It is also possible for you to set an instance directly, via the instances property.

// Your class
class Box {
    // ... implementation not shown .../
}

let box = new Box();
IoC.instances.set('my-box', box);

// Later ...
let myBox = IoC.make('my-box');

Aliases

Once you have bound a resource, you can also assign an alias for it. This can be useful in situations where your resource needs to be resolved / obtained via different identifiers.

// Binding first
IoC.bind('my-box', (ioc, params) => {
    // ... not shown .../
});

// Alias
IoC.alias('my-box', 'largeBox');

// Later...
let largeBox = IoC.make('largeBox');

Resolving nested dependencies

To the extend of my knowledge, one cannot gain insight of what object or "scalar" types are expected by a class or method, using plain JavaScript. Therefore, in order to resolve nested dependencies, this Service Container makes use of "mata data", which can be assigned to any class or object.

In the following example, image that you have a class has a dependency. There are several ways that you can resolve it. However, if you need the IoC to resolve that dependency automatically, then you need to provide a bit more information when binding.

// Class A
class DimensionsCalculator {
    // ... implementation not shown ... //
}

// Class B
class Box {

    /**
     * @param {DimensionsCalculator} calculator
     */
    constructor(calculator){
        this.calculator = calculator;
    }
    
    // ... remaining not shown ... //
}

// Bind the calculator via callback (just as an example)
IoC.bind('calculator', (ioc, params) => {
    return new DimensionsCalculator();
});

// Bind the Box class - specify it's expected dependencies
IoC.bindInstance('my-box', Box, false, [
    '@ref:calculator'       // '@ref:' prefix MUST be present!
]);

// Later...
let box = IoC.make('my-box');

console.log(box.calculator); // DimensionsCalculator{}

Basically, any class or object that has "meta data" defined, with dependencies (@ref: prefixed), the IoC will attempt to resolve those dependencies.

For more information, please review the source code and the "mata data" package.

Delete Bindings

Sometimes it can be useful to remove (delete) bindings again. This is especially true, when you are writing various executable tests.

Remove a single binding

IoC.forget('my-box');

Remove ALL bindings

IoC.flush();

Contribution

Have you found a defect ( bug or design flaw ), or do you wish improvements? In the following sections, you might find some useful information on how you can help this project. In any case, I thank you for taking the time to help me improve this project's deliverables and overall quality.

Bug Report

If you are convinced that you have found a bug, then at the very least you should create a new issue. In that given issue, you should as a minimum describe the following;

• Where is the defect located
• A good, short and precise description of the defect (Why is it a defect)
• How to replicate the defect
• (A possible solution for how to resolve the defect)

When time permits it, I will review your issue and take action upon it.

Fork, code and send pull-request

A good and well written bug report can help me a lot. Nevertheless, if you can or wish to resolve the defect by yourself, here is how you can do so;

• Fork this project
• Create a new local development branch for the given defect-fix
• Write your code / changes
• Create executable test-cases (prove that your changes are solid!)
• Commit and push your changes to your fork-repository
• Send a pull-request with your changes
• Drink a Beer - you earned it :)

As soon as I receive the pull-request (and have time for it), I will review your changes and merge them into this project. If not, I will inform you why I choose not to.

Acknowledgement

• Taylor Otwell, for his Service Container, that I'm using daily

Versioning

This package follows Semantic Versioning 2.0.0

License

BSD-3-Clause, Read the LICENSE file included in this package