Angular 6 Services: providedIn: 'root' vs CoreModule
With Angular 6, below is the preferred way to create singleton services:
import { Injectable } from '@angular/core';
@Injectable({
providedIn: 'root',
})
export class UserService {
}
From Angular doc: When you provide the service at the root level, Angular creates a single, shared instance of HeroService and injects into any class that asks for it. Registering the provider in the @Injectable metadata also allows Angular to optimize an app by removing the service if it turns out not to be used after all.
Also,
providers: [
// no need to place any providers due to the `providedIn` flag...
]
So, does that mean we no more need CoreModule? We can import services and other common modules directly into AppModule.
Answer
Well I would consider it as an alternative to creating a CoreModule, the documentation clearly states:
There are two ways to make a service a singleton in Angular: Declare root for the value of the @Injectable() providedIn property
Include the service in the AppModule or in a module that is only imported by the AppModule
I found this here Singleton Services doc
If you app has a CoreModule of pure services you could simply get rid of it(if you don't think is necessary of course), although I don't recommend it, for me I consider it more mantainable to have a CoreModule because I can easily find it in the project and tells me what services are fundamental for the app and we need only one instance from them, instead of having to open a search dialog in the IDE and look for all the services that have the providedIn: 'root' setted.