Rx - catch

  getData(id : number) : Observable<Post> {
    return this.http.get(${this.requestUrl}/${id})
      .map(this.mapResponse)
      .catch(this.handleError)
  }

  handleError(error: any): Observable<any> {
    console.error('An error occurred', error);
    return Observable.throw(error.json() || 'Server error');
  }

The catch reference is there to handle exceptions that are thrown. This gives you an opportunity to handle them in a graceful manner.
All rx operations return an observable.

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