Angular 2 subscribing to a service which is subscribed to another async function

Question

I am trying to develop an Angular application where there is a situation I am calling a service that is subscribed to HTTP service. I have written an alert prompt service which internally calls the HTTP service when "ok" is pressed. Like this:

this.alertservice.prompt(url);

This will prompt the user for confirmation. If the user clicks "ok", the alert service will call the HTTP service internally:

this.httpservice.get(url).subscribe(res => {
  console.log(res);
});

Now I want to inform the parent caller whether the call failed or succeeded. Something like:

 this.alertservice.prompt(url).subscribe(res => {
   console.log("success or failure");
 });

But I am not understanding how to subscribe to the alert function. How do I do this?

Answer 1

maybe something like:

import {..., EventEmitter} from '@angular/core';

export class AlertService {

     ...

     prompt(url:string): Observable<boolean> {

         let result = new EventEmitter<boolean();

         this.httpService.get(url).subscribe
             (
             (res) => {
               console.log("OK:", res);
               result.emit(true);
               result.complete();
             },
             (error) => {
               console.log("ERROR:", error);
               result.emit(false);
               result.complete();
             }
         );
         return result;
     }
}

now you can subscribe to the prompt()-function:

this.alertService.promp(url).subscribe((okOrNotOk) => {
     // okOrNotOk will be true, when the url was retrieved successfully, 
     // otherwise false
});

I'm not an expert on rxjs, perhaps there is a better way to do this.