Why these RxJS operators are not running in my function?-CodePudding

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 ?

CodePudding user response：

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.