Why these RxJS operators are not running in my function?

Question

I wrote a function to check if a div should be displayed, like this :

 shouldShowDiscount() {
    console.log('shouldShowDiscount');
    return this.baseSiteService.getActive().pipe(
      switchMap(
        (bucode, index) => {
          console.log('bucode', bucode);
          if (bucode == 'wtcph') {  
            return this.cartService.getActive().pipe(
              tap(cart => {
                console.log('cart', cart);
                 (cart?.customerGroupDiscountType == 'SC'
                  || cart?.customerGroupDiscountType == 'PWD') 
                  ? this.hostClass.push('') 
                  : this.hostClass.push('hide');             
                }
              )
            )
          }
        }
      )
    );
  }

I put the function in ngOnInit :

ngOnInit() {
    this.shouldShowDiscount();
}

However only the first console.log() before the return runs, the logs inside the operators won't run.

if I change the function call and add .subscribe() then the console.logs will all run :

ngOnInit() {
    this.shouldShowDiscount().subscribe(res => {
console.log(res)
});

}

is there a way to get it to work without the subscribe ?

In short, no. Either you subscribe or some library subscribes on your behalf. — Mrk Sef
– Mrk Sef, Commented Aug 2, 2022 at 13:47

Yozmo · Accepted Answer · 2022-08-02 03:40:58Z

2

Maybe you should have a look at Observables. The idea is that they emit values, but only when there is a Observer to watch them. With subscribe you trigger that. Without calling subscribe to an Observable, he’ll never emit any value.

Note: be aware of the fact that every time you subscribe to an observable you have to close that subscription at some point, otherwise you’ll have memory leak.

edited Aug 2, 2022 at 3:40

answered Aug 2, 2022 at 3:31

Yozmo

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