zombiebox-extenstion-dependency-injection

ZombieBox extension that adds Dependency Injection support.

It operates by scanning application source code, finding injection targets and services that provide classes and, building dependency graph and generating a BaseServiceContainer class that handles their initialization, cross-dependencies and populates targets properties with injection values.

Configuration

``js
module.exports = () => ({
extensions: {
di: {
services: { / Dictionary of explicitly configured services / },
servicesAutodetect: [ / Array of service detection roots /]
}
}
})
`

Services

Services are classes that are meant to be injected. They are listed in config either explicitly, or as part of automatic detection roots.

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Explicit services are configured under extensions.di.services filed as an object with its keys being services names and values – objects configuring the way service should be instantiated and its dependencies.

Configuration fields are:

* _class – service class name
* _import – ImportType ("default" or "partial"), the way ES6 modules should be imported
* _path – path to file with this class declaration
* _group - semantic group this service will be put into

The rest of the keys are dependencies of this service.

Example:
`js
movie: {
_class: 'Movie',
_group: 'controller',
_import: ImportType.DEFAULT,
_path: '/controllers/movie/movie.js',
sceneMovieCard: '{MovieCard}',
sceneMovieList: '{MovieList}',
repositoryMovie: '@repositoryMovie'
}
`

This declares that:

* MovieController class should imported from /controllers/movie/movie.js and constructed in service container
* It can be imported as default import
* Its instance should be named movie
* And placed into controller namespace
* It depends on repositoryMovie service
* It depends on MovieCard and MovieList classes

And will generate BaseServiceContainer class with the following structure (simplified):

`js
// .generated/dependency-injection/base-service-container.js
import Movie from '/controllers/movie/movie.js';

export default class{
constructor() {
this.movie = new MovieController();
}
}
`

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Services can be automatically detected under service roots declared in servicesAutodetect config key.
The default value for this field contains scenes and service folders.

Root entry can either be a string, or object with fields group and directory


`js
{
group: 'string',
directory: 'string'
}
`

Dependency detection

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Public class properties with type annotation comment starting with :inject:

`js
class MovieController {
constructor() {
/**
* @type {MovieList}:inject
*/
this.sceneMovieList;
}
}
`

or:

`js
/**
* @type {MovieList}:inject
*/
MovieController.prototype.sceneMovieList;
`

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Methods with parameters that have their description start with :inject

`js
class MovieController {
/**
* @param {MovieList} sceneMovieList :inject
*/
setSceneMovieList(sceneMovieList) {
this._sceneMovieList = sceneMovieList;
}
}
`

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Constructor parameters that have their description start with :inject

`js
class MovieController {
/**
* @param {MovieList} sceneMovieList :inject
* @param {MovieCard} sceneMovieCard :inject
*/
constructor(sceneMovieList, sceneMovieCard) {
this._sceneMovieList = sceneMovieList;
this._sceneMovieCard = sceneMovieCard;
}
}
``

Dependency matching

Dependency injection will match classes as following:

* Class exactly matching declared dependency
* Class inheriting from declared dependency
* Class implementing interface declared in dependency

If there are several classes matching declared dependency there's no guarantee which one will be injected.