How to get last value when subscribing to an Observable?

Question

I have two Angular2 components which need to share data via a service:

@Injectable()
export class SearchService {
           


        

Answer 1

You can use the ReplaySubject to always get the last value of the Observer, something like this :

@Injectable()
export class SearchService {

  private searchResultSource = new ReplaySubject<string>(1);

  setSearchResults(_searchResult: string): void {
      this.searchResultSource.next(_searchResult);
  }
}

And just subscribe as normal.
A more advanced example can be found here : caching results with angular2 http service

Answer 2

BehaviorSubject immediately emits the last value to new subscribers:

@Injectable()
export class SearchService {

  private searchResultSource = new BehaviorSubject<string>('');

  setSearchResults(_searchResult: string): void {
      this.searchResultSource.next(_searchResult);
  }
}

ReplaySubject emits all previous events to new subscribers.