datastore-get-only.ts

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { BehaviorSubject} from 'rxjs';
import { StoreSettings } from './models/store-settings.model';

@Injectable({ providedIn: 'root' })
export abstract class StoreService<T> {
  protected itemsSubject = new BehaviorSubject<T[]>([]);
  items$ = this.itemsSubject.asObservable();

  protected get items(): T[] {
    return this.itemsSubject.getValue();
  }
  protected set items(val: T[]) {
    this.itemsSubject.next([...val]);
  }

  constructor(
    protected http: HttpClient,
    protected settings: StoreSettings
  ) {}

  load() {
    const url = this.settings.url;

    this.http
      .get<T[]>(url)
      .subscribe((res) => {
        this.items = res;
      });
  }
}