CODEWITHSUNDEEP
angularrxjs6
Yasha Gasparyan
Yasha Gasparyan

Reputation: 400

Combine observable with multiple observables

Here I want to combine values from observables. This code works, but nesting subscribes in such fashion is not good. I'm looking for better solutions. Thanks in advance.

someObservable().subscribe(
      data => {                      // array of elements
        data.forEach(
          element => {
            anotherObservable(element.id)
              .subscribe(
                anotherData => doSomething(data, anotherData); // both data needed
              );
          }
        );
      }
    );

Upvotes: 0

Views: 560

Answers (2)

Sanjay Lohar
Sanjay Lohar

Reputation: 528

You can use merge for it

Click here for Official Doc

Eg:-

// RxJS v6+
import { mapTo } from 'rxjs/operators';
import { interval, merge } from 'rxjs';

//emit every 2.5 seconds
const first = interval(2500);
//emit every 2 seconds
const second = interval(2000);
//emit every 1.5 seconds
const third = interval(1500);
//emit every 1 second
const fourth = interval(1000);

//emit outputs from one observable
const example = merge(
  first.pipe(mapTo('FIRST!')),
  second.pipe(mapTo('SECOND!')),
  third.pipe(mapTo('THIRD')),
  fourth.pipe(mapTo('FOURTH'))
);
//output: "FOURTH", "THIRD", "SECOND!", "FOURTH", "FIRST!", "THIRD", "FOURTH"
const subscribe = example.subscribe(val => console.log(val));

Upvotes: 1

Adrita Sharma
Adrita Sharma

Reputation: 22213

You can use mergeMap for it

Like this:

return this.someObservable().pipe(
  mergeMap(element=> this.anotherObservable(element.id).pipe(
    map(anotherData => {
      return {
        res1: element ,
        res2: anotherData 
      }
    })
  ))
)

Upvotes: 2

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