javascript - Angular 2 - Handling multiple subscriptions on a single observable -

i'm working on angular 2 app , need guidance on how handle authentication errors cleanly.

my end goal able centrally handle authentication errors (specifically 401 , 403) every http request.

i found this question super helpful getting me started, i'm stuck proper way register error handler each observable returned custom http implementation.

here sample of i'm working with:

    import {injectable} 'angular2/core';     import {http, connectionbackend, request, requestoptions, requestoptionsargs, response} 'angular2/http';      import {observable} 'rxjs/observable';       @injectable()     export class clauthhttp extends http {      constructor(backend: connectionbackend, defaultoptions: requestoptions) {         super(backend, defaultoptions);     }      get(url: string, options?: requestoptionsargs): observable<response> {         var response = super.get(url, options);          return this._handlesecurityresponse(response);     }      /*     other overrides omitted brevity...     */      private _handlesecurityresponse(response: observable<response>):     observable<response> {         response.subscribe(null, (error: response) => {             // nifty error handling here.         });          return response;     } } 

the above solution "works" 1 hitch... every http request made twice. that's no good.

any guidance on how this?

(update) working code

based on information in accepted answer here class looks in functioning form.

    import {injectable} 'angular2/core';     import {http, connectionbackend, request, requestoptions, requestoptionsargs, response} 'angular2/http';      import {observable} 'rxjs/observable';     import 'rxjs/add/operator/share';       @injectable()     export class clauthhttp extends http {      constructor(backend: connectionbackend, defaultoptions: requestoptions) {         super(backend, defaultoptions);     }      get(url: string, options?: requestoptionsargs): observable<response> {         var response = super.get(url, options);          return this._handlesecurityresponse(response);     }      /*     other overrides omitted brevity...     */      private _handlesecurityresponse(response: observable<response>):     observable<response> {         var sharable = response.share();          sharable.subscribe(null, (error: response) => {             // nifty error handling here.         });          return sharable;     } } 

this due fact observable<response> cold observable, i.e. 'restarted' every new subscriber. explanation of hot vs. cold observables, have @ hot , cold observables : there 'hot' , 'cold' operators?. here subscribe once result handler, , time error handler.

you should able workaround subscriptions side effect 'sharing' observable,

i.e. replace

var response = super.get(url, options); 

with

var response = super.get(url, options).share();`