Retain the type of mutiple Observable<T> using combineLatest() from rxjs under Angular?

First things first, you have to type your function and your HTTP call.

getMonkey(): Observable<Donkey> {
  return this.http.get<Donkey>(url);
}

Once done, you have to type your array of observables :

const observables: [Monkey, Donkey] = [
  this.getMonkey(),
  this.getDonkey(),
];

Finally, although not necessary, you can type your callback params :

forkJoin(observables).subscribe(([monkey, donkey]: [Monkey, Donkey]) => {...});

This sounds like a use case for tuples. https://visualstudiomagazine.com/articles/2016/02/01/type-safe-structures.aspx?m=1

type animalTuple = [Donkey, Monkey];

.subscribe(([donkeyResult, monkeyResult]: animalTuple) => { ... }

Related