Dependency Injection in JavaScript/ES6
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README.md

diyai

Dependency Injection (DI) made easy in JavaScript/ES6

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Installation

With npm:

$ npm install --save diyai

With unpkg CDN:

<script src="https://unpkg.com/diyai@0.x/dist/diyai.min.js"></script>
<script>
 // now available in `window.Diyai`
</script>

Usage

Direct values

Let's start by defining a simple container first.

When defining the providers, we can directly assign values for them via the useValue key.

import { createContainer, resolveContainer } from 'diyai';

const Container = createContainer([
  { name: 'foo', useValue: 'foo value' },
  { name: 'bar', useValue: 'bar value' }
]);

Now, let's resolve it to get the Container's instance:

const container = resolveContainer(Container); // same as `new Container()`

Once resolved, you can get instaces of your providers as follows:

container.get('foo'); // `foo value`
container.get('bar'); // `bar value`

If there is any chance of having a cyclic reference, you can use useDefinedValue:

const myObj = {};

const Container = createContainer([
  { name: 'myObj', useDefinedValue: myObj }
]);

myObj.container = resolveContainer(Container);

Doing so would set a self-refernce of myObj in myObj.container.registry.myObj using Object.defineProperty via a getter function.

Values from factories

We can also pass functions in the Container definition for the providers, and their returned values will be used as the actual value then.

For that, we will use the useFactory key:

import { createContainer, resolveContainer } from 'diyai';

const Container = createContainer([
  { name: 'foo', useFactory: () => 'foo value' },
]);

const container = resolveContainer(Container);
container.get('foo'); // `foo value`

Classes

Some providers can even be classes, and can be passed in the Container definition in useClass key.

Once resolved, the container would then return the instance of the class.

Classes can be just plain ES6 classes:

class Foo {
  text() {
    return 'foo text'
  }
}

Or, they can be created with the handy createClass function shipped with this library:

import { createClass } from 'diyai';

const Foo = createClass({
  text: function () {
    return 'foo text';
  }
});

Once the class is written, we can define our container:

const Container = createContainer([
  { name: 'foo', useClass: Foo }
]);

Which can now be resolved as follows:

const container = resolveContainer(Container);

const fooInstance = container.get('foo');
fooInstance.text(); // `foo text`

Dependencies

Dependencies can be handled while defining the providers.

Let's say you have a Foo and Bar classes, and Bar depends on Foo:

class Foo {
  text() {
    return 'foo text';
  }
}

class Bar {
  constructor({ foo }) { // instance of Foo is given as constructor argument
    this.foo = foo;
  }

  fooText() {
    return this.foo.text();
  }
}

Once we have them as classes, we can pass them on to our container definition as follows:

const Container = createContainer([
  { name: 'foo', useClass: Foo },
  { name: 'bar', useClass: Bar, deps: ['foo'] }
]);

We are telling our Container that when bar is instantiated, pass the instance of foo to its constructor.

const container = resolveContainer(Container);

const bar = container.get('bar');
bar.fooText(); // `foo text`

The deps key can also be provided as an object instead of an array, where the keys are the container's provider names, and values are the names the target class is expecting.

API

createClass(extend = {})

Creates and returns a class.

import { createClass } from 'diyai';

const MyClass = createClass({
  initialize(deps) {
    // `deps` contains injected dependencies if any.
    // Should be treated as constructors of ES6 classes.
  },

  someMethod() {
    return true;
  }
});

resolveContainer(Container)

Returns instance of resolved container.

createContainer(providers = [], options = {})

Creates and returns a container class.

providers

An array of providers.

A single provider object would contain:

{
  name: 'uniqueNameHere',

  // and one of the following keys
  useValue: 'direct value of any type', // OR
  useFactory: () => 'returned value of any type', OR
  useClass: SomeClass, // created via `createClass` or ES6 classes

  // if `useClass` or `useFactory` is used, then `deps` can be provided
  deps: ['depName1', 'depName2', ...]

  // `deps` can also be an object:
  deps: { nameInContainer: 'nameExpectedInArgs' }
}

options

  • containerName: defaults to container.

This means, the container instance itself can be obtained as:

container.get('container'); // `container` instance

Thanks

  • Angular 2: For their Injector, since this project is an implementation of that in ES6 with no external dependencies.

License

MIT © Fahad Ibnay Heylaal