Recently I’ve been working with Angular 2/4. One day I came across with something like this:

public getCustomersOnArea(zip:string):Observable<Customer>{..}

The problem was that we had to make 2 calls to get the data. Even more one call depended on the data fetched from the other. How to solve this? One way it’s to encapsulate the 2 calls into a third one and return that to be subscribed.

public getCustomersOn(zip:string):Observable<Customer>{

return new Observable<Customer>(subscriber => {
            this.http.post(zip)
                .subscribe(res => {
                    this.http.post(res)
                        .subscribe(r => {
                            subscriber.next(r);                           
                        },
                          e=>  subscriber.error(e),
                          ()=>  subscriber.complete());
                });
}

And that’s it. Do you know another way? Leave it in the comments section