Verify objects in array also exist in observable array

Question

I would like to verify that the objects in the following array:

const payment1: Payment = new Payment('1000'); // 1000 = id
const payment2: Payment = new Payment('1001');

const paymentArray: Payment[];
paymentArray.push(payment1, payment2);

exist in my observable array:

payments$: Observable<Payment[]>;

What i would like is to get a non observable boolean as result.

I have tried somethings with filter pipe and map but unfortunately cant get it to work:

this.paymentArray.forEach(element => {
  this.payments$.pipe(map(payments => payments.filter(payment => payment.id === element['id'])));
});

rijin · Accepted Answer · 2019-09-17 11:39:01Z

1

if its array of objects, create a map of those elements to compare it in filter function.

ngOnInit() {

    this.idsToFind = ['1000', '1231', '2323'];
    const paymentArray: Payment[] = [];
    const payment1: Payment = new Payment('1000'); // 1000 = id
    const payment2: Payment = new Payment('1001');

    paymentArray.push(payment1, payment2);

    this.payments$ = of(paymentArray);

    const idsMap = this.idsToFind.reduce(
      (a, b) => { return { ...a, [b]: true } }, {}
    );
    console.log(idsMap);

    this.payments$
      .pipe(
        map((payments) =>
          payments.filter(
            (payment: Payment) => idsMap[payment.id])
        )
      )
      .subscribe((missings) => console.log(missings));

  }

answered Sep 17, 2019 at 11:39

rijin

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Comments

Ben · Accepted Answer · 2019-09-17 11:22:44Z

You can do something like this, see also my stackblitz link: https://stackblitz.com/edit/angular-yg1b11

import { Component, OnInit } from '@angular/core';
import { Observable, of } from 'rxjs';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  payments$: Observable<Payment[]>;
  idToFind = '';
  isFounded = false;

  ngOnInit() {

    this.idToFind = '1000'
    const paymentArray: Payment[] = [];
    const payment1: Payment = new Payment('1000'); // 1000 = id
    const payment2: Payment = new Payment('1001');

    paymentArray.push(payment1, payment2);

    this.payments$ = of(paymentArray);

    this.payments$.subscribe((x) => {
      x.forEach(element => {
        if (element.id == this.idToFind) {
          this.isFounded = true;
        }
      })
    })

  }

}

export class Payment {
  id: string;

  constructor(id: string) {
    this.id = id;
  }

}

Stanislav Dontsov · Accepted Answer · 2019-09-17 11:34:53Z

1

You can use toPromise to get observable result, like this:

const payment1: string = '1000';
const payment2: string = '1001';

const paymentArray: string[] = [];
paymentArray.push(payment1, payment2);

const payments$ = of(['1000', '1001', '1002']);

const allExist = await from(paymentArray).pipe(withLatestFrom(payments$), every(([item, payments]) => payments.includes(item))).toPromise();

answered Sep 17, 2019 at 11:34

Stanislav Dontsov

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Comments

31piy · Accepted Answer · 2019-09-17 12:12:49Z

1

You just need to pipe through the observable and map the stream. In the callback of map, check if every item paymentArray exists in the value.

See the following example:

const ids = paymentArray.map(p => p.id);

this.payments$.pipe(
  map(payments => {
    const paymentIds = payments.map(p => p.id);
    return ids.every(id => paymentIds.includes(id));
  })
)
// `value` should print `true` or `false` based on the checks.
.subscribe(value => console.log(value));

answered Sep 17, 2019 at 12:12

31piy

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