Undefined Perception

Trying to obtain values from an observable, my subscription code within the component looks like this:

this.checkoutService.getDisabledDate().subscribe
(dates=>{this.formattedDate=dates}, 
(error:any)=>{console.log(error)});

When logging this.formattedDate in the 'dates' callback, it correctly shows the values. However, trying to access this.formattedDate outside of the subscription results in undefined.

This is the service code:

getDisabledDate():Observable<any>{
    let headers = new Headers({'Content-Type': 'application/json' });
    let options = new RequestOptions({headers:headers});
    let userRequest={action_id:0};
    let disabledDate={};

    return this.http
        .post(this.deliveryUrl,userRequest,options)
        .map((r:Response)=>r.json())
        .catch(this.handleError);
}

I attempted the same process by passing data through a queryParam using short form (), but it did not make any difference. It seems I am missing something crucial in order to extract the information with this method.

I've referred to the following resources for help: Angular2 HTTP using observables subscribe showing data undefined and Angular 2 return data from service is not availabe after RxJs subscribe.

Despite going over these threads, I still cannot figure out what I am overlooking. Any ideas on what I might be missing?

Answer №1

It's not clearly specified in your inquiry where "outside" refers to, but if it pertains to a point after the function call that retrieves the Observable, then the behavior you are experiencing is anticipated.

function someMethod() {
  this.checkoutService.getDisabledDate()
  .subscribe(
    // any code placed here is executed at a later stage when the response from the server is received
    dates=>{ 
      this.formattedDate=dates;
      // additional logic dependent on the result goes here
    }, 
    (error:any)=>{console.log(error)}
  );
  // this part is processed first
}

You are unable to access the value outside of the subscribe function. One option is to utilize map and return the outcome for the caller to subscribe to, similar to what is done in getDisabledDate, or relocate the code within one of the callbacks.

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