Angular check if item is in Observable array with Rxjs operators

Question

I have a function that selects an offer, but I need to check whether this offer is in the Observable array of offers$ first.

selectOffer(offer) {
    this.offers$.subscribe(items => {
      items.forEach(item => {
        if (item === offer) {
          // if offer is in offers$, DO...
        }
      });
    });
  }

How could I transform this to work with Rxjs operators (pipe, map, filter etc..)

What's wrong with what you have now? Or you want to have an Observable that emits true/false based on whether the item is in the array? — martin
– martin, Commented Dec 17, 2019 at 9:57
We'll need more code. What do you expect the selectOffer to return? What kind of observable is this.offer$. — Poul Kruijt
– Poul Kruijt, Commented Dec 17, 2019 at 10:09

A. Gladkiy · Accepted Answer · 2019-12-17 10:52:23Z

2

Try find operator

Emit the first item that passes predicate then complete.

selectOffer(offer) {
    this.offers$.pipe(find((item: any) => item === offer)).subscribe(items => {
        console.log("Offer is in the list")
    });
}

edited Dec 17, 2019 at 10:52

A. Gladkiy

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answered Dec 17, 2019 at 10:14

Ininiv

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Comments

A. Gladkiy · Accepted Answer · 2019-12-17 10:52:51Z

1

You can use .map on observables

Try like this:

selectOffer(offer) {
  this.offers$.map(item => item.filter(x => x === offer));
}

edited Dec 17, 2019 at 10:52

A. Gladkiy

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answered Dec 17, 2019 at 9:58

Adrita Sharma

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Comments

AgedPeanuts · Accepted Answer · 2019-12-17 10:46:26Z

0

After trying several options, this one seemed the most effective for my case:

this.offers$
      .pipe(
        map(items =>
          items ? items.filter((item: any) => item === offer) : null)
      )
      .subscribe(item => { /* DO */ });

answered Dec 17, 2019 at 10:46

AgedPeanuts

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