example-observable-subject-competition-service.ts

export class CompetitionsService {

    // Create a Subect to observe
    private _competitionsSource:Subject<Competition[]> = new Subject<Competition[]>();

    // Publicly expose the Observable - called share() to allow multiple observers
    competitionsChanged$:Observable<Competition[]> = this._competitionsSource.asObservable().share(); 

    constructor(private _http:Http) {
        _http.get('http://localhost:8080/competitions')
            .map(res => res.json())
            .subscribe(
                data => {
                    // Call next() on on your source to propagrate to observers 
                    this._competitionsSource.next(data)
                },
                err => console.error('Failed to load competitions', err),
                () => console.log('Loaded competitions')
            );
    }

}