Angular-Style Injector

A lightweight dependency injection container inspired by Angular's Injector.

Installation

npm install angular-style-injector

Preconditions

Before you start using this package, make sure to complete the following steps:

1. Import reflect-metadata once in your entry point .ts file (main.ts or maybe index.ts):

import 'reflect-metadata';

2. Add these two essential parameters to your tsconfig.json file:

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

Usage

import { Injector, Injectable, InjectionToken } from 'angular-style-injector';

@Injectable()
class DependencyOne {
  readonly description = 'Dependency one';
}

@Injectable()
class DependencyTwo {
  readonly description = 'Dependency two';
}

@Injectable()
class Parent {
  readonly description = 'Parent';

  constructor(
    readonly depOne: DependencyOne,
    readonly depTwo: DependencyTwo,
  ) {}
}

const CLASS_TOKEN = new InjectionToken<Parent>('Class token');
const VALUE_TOKEN = new InjectionToken<number>('Value token');
const FACTORY_TOKEN = new InjectionToken<string>('Factory token');
const EXISTING_TOKEN = new InjectionToken<number>('Existing token');

const injector = Injector.create({
  providers: [
    DependencyOne,
    DependencyTwo,
    { provide: CLASS_TOKEN, useClass: Parent },
    { provide: VALUE_TOKEN, useValue: 10, multi: true },
    { provide: VALUE_TOKEN, useValue: 20, multi: true },
    { provide: EXISTING_TOKEN, useExisting: VALUE_TOKEN },
  ],
  parent: Injector.create({
    providers: [
      DependencyTwo,
      {
        provide: FACTORY_TOKEN,
        useFactory: (depTwo: DependencyTwo) => depTwo.description,
        deps: [DependencyTwo],
      },
    ],
    name: 'Parent injector',
  }),
  name: 'Origin injector',
});

console.log(
  injector.get(CLASS_TOKEN), // instance of Parent class
  injector.get(VALUE_TOKEN), // Array: [10, 20]
  injector.get(FACTORY_TOKEN), // String: 'Dependency two'
  injector.get(EXISTING_TOKEN), // Array: [10, 20]
);