Preserving class encapsulation by providing methods to interact with Subjects

encapsulated-subjects.ts

class DataService {
  private pokemonLevel = new BehaviorSubject<number>(1);
  private stop$: Subject<void> = new Subject();

  pokemonLevel$ = this.pokemonLevel.asObservable();

  increaseLevel(level: number) {
    if (!this.isValidLevel(level)) {
      throw new Error("Level is not valid");
    }

    this.pokemonLevel.next(level);
  }

  stop() {
    this.stop$.next();
  }

  private isValidLevel(level: number): boolean {
    return level % 2 === 0;
  }
}