Wait for observable to get array-data

Question

I know there have been several questions regarding this, but I havent found a way that works for me properly. If you find one gladly send it to me.

So I am getting my data from an API and I convert this data into an array of my required datatype:

getData(): Observable<Type[]> {
    return this.http.get<Type[]>("URL)
      .pipe(
        retry(2),
        catchError(this.handleError)
      );
  }

I want to use the data, after I got it.

Some ways i tried to solve this were with while(empty){...} which seems to be unefficient and not correct if the array is empty, Promises where I didn't really find a way to connect properly with observables and await/async which seems to be impossible with observables.

My code of implementing this:

array: Type[] = [];
useJSON(searchString: string) {
    this.configService.getData().subscribe(results => { this.array = results});
    // --operations--
  }

So you want to listen as long as some particular array will come ? await/async can be used with promises (and observables can be promises ) — Antoniossss
– Antoniossss, Commented Jul 24, 2020 at 8:06
It is not impossible to use async/await with observables. If you are sure it is emitted just once you can always convert it to a promise. But if you want it to keep the observable way, you need to do your "further operations" in your pipe. — Eldar
– Eldar, Commented Jul 24, 2020 at 8:09
What do you mean by I do need to perform some additional operations to use this data and I need to be sure that this array is already filled up with the whole data. ? Received data is immutable - it wont change over time - you have to make new request. My answer is for what Iv understand that you want to fetch some data over and over again until it meets some condition. — Antoniossss
– Antoniossss, Commented Jul 24, 2020 at 8:15
Ok, so I want to perform my operations which use the data, after I got it. — bena
– bena, Commented Jul 24, 2020 at 8:22
@bena: Do it inside the subscription. That's the correct way to do something over async variables obtained from observables. — Barremian
– Barremian, Commented Jul 24, 2020 at 8:23

Antoniossss · Accepted Answer · 2020-07-24 08:08:58Z

1

async/away should work for you (syntax might be slightly invalid)

youdMethod() async{
let res=null;

do{
 res=await this.configService.getData().toPromise();
}while(resBasedCondition)
 
}

what you probably wat is to have operator repeatIf but it is not available. Behavior can be mimic using expand as shown here https://stackoverflow.com/a/51644077/1527544

answered Jul 24, 2020 at 8:08

Antoniossss

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Barremian · Accepted Answer · 2020-07-24 08:10:47Z

1

I am not exactly sure what you're looking for. If you need to do further operations after the this.array is initialized, then include them inside the subscription after the assignment.

array: Type[] = [];
useJSON(searchString: string) {
  this.configService.getData().subscribe(results => { 
    this.array = results;
    // --further operations--
  });
}

answered Jul 24, 2020 at 8:10

Barremian

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