Angular2 merge part of objects

Question

I need to merge two same type observables and return same type observable in Angular2 function.
So all I want to do is:

from this:

obs1.subscribe(obs => console.log(obs))
(where I get): 
{
   count: 10,
   array: <someObservable[]> 
}

and

obs2.subscribe(obs => console.log(obs))
(where I get): 
{
   count: 10,
   array: <someObservable[]> (different objects)
}

into:

{
   count: 10 (count always the same number),
   array: <someObservable[]> (combined array from obs1 and obs2)
}

What is the simplest way to achieve that? (Maybe it is simple to even junior level angular developer, but I have to it quickly and Im newbie in this sphere). Thanks in advice.

---UPDATE---

from this code part :

const obs2 = obs1.pipe(
        switchMap(value => {
          return this._loadMoreTextSearchSub.asObservable()
          .pipe(pairwise(),
          map(params => this.getPagingParameters(params[0], params[1])),
          switchMap(request),
          map(response => response.packages),
          scan<SearchPackage[]>((all, current) => {
            return [...all, ...current];
          }, 
          value.packages
          ));
        }))
        .subscribe(data => console.log('sec', data));

I get array of objects. How could I wrap that array into the object and set extra property - 'count'?

Current:
[{...}, {...}, {...}, {...}]
Desired:
{count: some_number, array: [{...}, {...}, {...}]}

It depends on how do you want to call the observables, should they be called subsequently, parallely? — Ashish Ranjan
– Ashish Ranjan, Commented May 6, 2020 at 19:22

Ashish Ranjan · Accepted Answer · 2020-05-06 19:30:38Z

2

If you need to call the Observables subsequently then you can use mergeMap() for the same.

Lets say, you call obs1 first, once you have the result of obs1, you call obs2, then combine both the results and return.

obs1.pipe(mergeMap((firstResult) => {
    return obs2.pipe(map((secondResult) => {
        return { count: firstResult.count, array: [...firstResult.array, ...secondResult.array] };
    }))

})).subscribe((data) => {
    console.log(data);
})

answered May 6, 2020 at 19:30

Ashish Ranjan

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3 Comments

Karlito Over a year ago

Appreciate your help! Is it hard to rewrite code for parallely called observations?

Ashish Ranjan Over a year ago

@Karlito Nope, its all the same. You have forkJoin(), combineLatest(), withLatestFrom(), zip(), etc. You can use any of them, depending on your requirement. Just the ways of using them are different.

Ashish Ranjan Over a year ago

@Karlito See this link: scotch.io/tutorials/… .Its very nicely explained for some of them'.

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