angular2 provider aliases

my-providers.ts

import { Component, NgModule, Provider, ClassProvider, FactoryProvider,
         TypeProvider, ValueProvider } from '@angular/core';

import { MyThingDoer } from './my-thing-doer.service.ts';


@NgModule({
  providers: [
    MyThingDoer,
    { provide: MyThingDoer, useClass: MyThingDoer },
    { provide: MyThingDoer, useValue: new MyThingDoer() },
    { provide: MyThingDoer, useFactory: () => new MyThingDoer() },
    { provide: MyThingDoer, useFactory: function() { return new MyThingDoer(); } },
  ]
})
export class MyProvidersModule {}


// why is that all equivalent? let's rewrite the stuff even more explicit:

const typeProvider: TypeProvider
  = MyThingDoer;

const valueProvider: ValueProvider
  = { provide: MyThingDoer, useValue: new MyThingDoer() };

const classProvider: ClassProvider
  = { provide: MyThingDoer, useClass: MyThingDoer };

const factoryProvider: FactoryProvider
  = { provide: MyThingDoer, useFactory: function() { return new MyThingDoer(); } };

const myProviders: Provider[] = [
  typeProvider,
  valueProvider,
  classProvider,
  factoryProvider,
];

@Component({
  providers: myProviders
})
export class MyComponent {}