RxJs Data Cache

LookupDataStore.ts

/**
 * Provides a cache of look up data
 *
 * consumers can subscribe or use async-pipe to get the list of lookup values in each category
 *
 * shareReplay(1) will make it so that each subscriber gets the last emitted value rather than making
 *                another API call
 * take(1)        is just a convenience for the consumers in case they forget to unsubscribe it will
 *                only emit once and then complete, to avoid a memory leak
 */
export class LookupDataStore {
  constructor(private readonly api: ApiService) { }

  public readonly countries$ = this.api.getLookupData('countries').pipe(shareReplay(1), take(1));
  public readonly userRoles$ = this.api.getLookupData('userRoles').pipe(shareReplay(1), take(1));
}