Q:

Angular 2 Observable subscribe not working

I am trying to subscribe to an observable on init of a component like so:
    this.ticketService.getTicketsAsync(filters).subscribe(
        tickets => this.ticketResponse = tickets,
        () => console.log('hi'))

Is there any reason why the first lambda expression works, but the second one never does? 
EDIT:
Here is the code hat getTicketAsync is returning:
getTicketsAsync(ticketFilters : TicketSearch): Observable<TicketResponse> {

    let api_endpoint = AppSettings.API_ENDPOINT + 'WebReport/request_report'
    let headers = new Headers({ 'Content-Type': 'application/json' });
    let options = new RequestOptions({headers : headers, withCredentials : true});
    return this.http.post(api_endpoint, ticketFilters, options).map(this.extractData).catch(this.handleError);

}

A:

The second one is catch when observable throw error.
subscription = source.subscribe(
  x => console.log('onNext: %s', x),
  e => console.log('onError: %s', e),
  () => console.log('onCompleted'));

https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/subscribe.md
Solution:
1. Use onNext hook:
this.ticketService.getTicketsAsync(filters).subscribe(
    tickets => {
      this.ticketResponse = tickets;
      console.log('hi');
    },
    () => console.log('ERROR!'));

2. Use onCompleted hook:
this.ticketService.getTicketsAsync(filters).subscribe(
  tickets => this.ticketResponse = tickets,
  error => console.log('ERROR: ' +error),
  () => console.log('hi')
);

