Here is a working example with Angular version 2.3. Just call the constructor of the service the stand way like this constructor(private _userService:UserService) . And it will create a singleton for the app.
user.service.ts
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Rx';
import { Subject } from 'rxjs/Subject';
import { User } from '../object/user';
@Injectable()
export class UserService {
private userChangedSource;
public observableEvents;
loggedUser:User;
constructor() {
this.userChangedSource = new Subject<any>();
this.observableEvents = this.userChangedSource.asObservable();
}
userLoggedIn(user:User) {
this.loggedUser = user;
this.userChangedSource.next(user);
}
...
}
app.component.ts
import { Component } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { UserService } from '../service/user.service';
import { User } from '../object/user';
@Component({
selector: 'myApp',
templateUrl: './app.component.html'
})
export class AppComponent implements OnInit {
loggedUser:User;
constructor(private _userService:UserService) {
this._userService.observableEvents.subscribe(user => {
this.loggedUser = user;
console.log("event triggered");
});
}
...
}