How to return from within an observer? - rxjs

Question

I was trying to return filter function but return doesn't seem to work with callbacks. Here this.store.let(getIsPersonalized$) is an observable emitting boolean values and this.store.let(getPlayerSearchResults$) is an observable emiting objects of video class.
How do I run this synchronously, can I avoid asynchronus callback altogether given that I can't modify the observables received from store.
isPersonalized$ = this.store.let(getIsPersonalized$);
videos$ = this.store.let(getPlayerSearchResults$)
.map((vids) => this.myFilter(vids));
myFilter(vids) {
this.isPersonalized$.subscribe((x){
if(x){
return this.fileterX(vids);//Return from here
}
else {
return this.filterY(vids);//Or Return from here
}
});
}
fileterX(vids) {
return vids.filter((vid) => vids.views>100;);
}
fileterY(vids) {
return vids.filter((vid) => vids.views<20;);
}

Answer 1

I got it working this way, you don't need myFilter(vids) at all if you can get the branching out on isPersonalized$'s subscribe. Here is the updated code.
this.store.let(getIsPersonalized$);
videos$: Observable<any>;
ngOnInit() {
this.isPersonalized$.subscribe((x) => {
if (x) {
this.videos$ = this.store.let(getPlayerSearchResults$)
.map((vids) => this. fileterX(vids));
} else {
this.videos$ = this.store.let(getPlayerSearchResults$)
.map((vids) => this. fileterY(vids));
}
});
}
fileterX(vids) {
return vids.filter((vid) => vids.views>100;);
}
fileterY(vids) {
return vids.filter((vid) => vids.views<20;);
}

Answer 2

It looks like you want to evaluate the latest value of isPersonalized$ within the map function, i'd do that via withLatestFrom (Example: The first one toggles true/false every 5s, the second emits an increasing number every 1s):
const isPersonalized$ = Rx.Observable.interval(5000)
.map(value => value % 2 === 0);
const getPlayerSearchResults$ = Rx.Observable.interval(1000)
.withLatestFrom(isPersonalized$)
.map(bothValues => {
const searchResult = bothValues[0];
const isPersonalized = bothValues[1];
...
});