Concat list and observable list-CodePudding

Let's say I have 3 lists. Two of them are basic lists while the last one is an observable.

The issue is I now want to merge a non-observable list into the observable one.
Right now I do something like this but I feel like it's "against observables' nature"

listToMerge = []
listObs$: BehaviorSubject<[]> = new BehaviorSubject([]);
listObsCopy = []

I already added some elements in the listObs with the next method

listObs$.next(someStuff);
listObsCopy = somestuff;

Here is my attempt to merge them.

listToMerge = listObsCopy.concat(someOtherStuff);
listObs$.next(listToMerge as any);

CodePudding user response：

You can easily create an observable from your array to then concat them using the from() function:

https://www.learnrxjs.io/learn-rxjs/operators/creation/from

const arraySource = from([1, 2, 3, 4, 5]);
const arraySource2 = from([6, 7, 8]);
arraySource.concat(arraySource2).subscribe()

CodePudding user response：

Is this what you're looking for? It will merge all arrays into a single one using RxJS.

    import { of, BehaviorSubject, merge } from 'rxjs';
    import { concatAll, take, tap, toArray } from 'rxjs/operators';

    let listToMerge = [];
    let listSubject: BehaviorSubject<string[]> = new BehaviorSubject<string[]>(['B1','B2',]);
    let listObs$ = listSubject.asObservable().pipe(take(1));
    let listObsCopy = [];

    // Give some content
    listObsCopy = ['Three', 'Four'];
    listToMerge = ['1', '2'];

    let mergedArray$ = merge(of(listObsCopy), of(listToMerge), listObs$).pipe(
      concatAll(),
      toArray(),
    );

    mergedArray$.subscribe((value) => console.log('merged array:', value));

The trick is in using concatAll() operator to flatten all arrays and then use toArray() operator to make 1 array out of that.

Note that I've added take(1) to the observable for the subject. The subscribe will only start when the Observable ends.