As of Angular 6, we have access to a great way to have our services globally available in our applications, while still being bundled and lazy loaded as efficiently as possible.
@Provider decorators now take an additional argument, providedIn.
In almost every case, you want to use providedIn: 'root' - telling your angular application that this service should be a singleton, available all throughout your application. You don't even need to inject it into a module!
app/greeter.service.ts
import { Injectable } from "@angular/core";
@Injectable({
providedIn: "root"
})
export class GreeterService {
private message: string =
"Registering Providers while Bootstrapping an Angular 2 application!";
getMessage() {
return this.message;
}
}