当主题是服务更改时在组件中重新加载列表 Angular 10

Question

我想在 component 中对列表进行更改时重新加载列表。此列表作为 BehaviourSubject 存储在 service 中。我订阅了我的组件中的主题，该主题在 table 中显示列表。当用户单击列表中的项目时，它会通过 router 打开一个视图。这是用户可以对该项目执行某些操作（删除、edit/save 等）的地方，但是当删除项目时，它会在 service 的原始列表中删除它，但它仍然显示显示列表的组件中的项目。我以为如果进行更改并重新加载列表，将检查行为主题，但它似乎不起作用。

我的service.ts:

export class OfferService {
  offers: Offer[] = [];
  public offersSubject = new BehaviorSubject<Offer[]>(this.offers);

  constructor(private http: HttpClient) {
    this.generateRandomOffers();
   }

  private generateRandomOffers(): void {

    for (let i = 0; i < 8; i++) {
      let offer = new Offer(this.offersSubject.getValue().length + 1);
      offer = Offer.createRandomOffer();
      this.offersSubject.getValue().push(offer);
    }

  }

  public FindAll(): Offer[] {
    return this.offersSubject.getValue();
  }

  // observable of offers list
  public getAll(): Observable<Offer[]> {
    return of(this.offersSubject.getValue());
  }


  public FindById(offerId: number): Offer {
    return this.offersSubject.getValue().find(o => o.id === offerId);
  }

  public Save(offer: Offer): Offer {
    let offerExist = false;
    const index = this.offersSubject.getValue().findIndex(o => o.id === offer.id);

    this.offersSubject.getValue().forEach( element => {
      if (element.id === offer.id)
      {
        element = offer;
        offerExist = true;
        this.offersSubject.getValue()[index] = element;
      }
    });

    if (!offerExist)
    {
      this.offersSubject.getValue().push(offer);
    }
    return this.offersSubject.getValue().find(o => o.id === offer.id);
  }

  public DeleteById(offerId: number): Offer {
    const deleteOffer = this.offersSubject.getValue().find(o => o.id === offerId);
    this.offers = this.offersSubject.getValue().filter(o => o.id !== offerId);
    this.offersSubject.next(this.offers);
    return deleteOffer;
  }

  public AddOffer(): void {
    let offer = new Offer(this.offers.length + 1);
    offer = Offer.createRandomOffer();
    this.offersSubject.getValue().push(offer);
  }
}

我的Component.ts（显示列表的地方）：

selectOfferViaRouter = false;
  offers: Offer[] = [];
  selectedOfferId = -1;
  trigger: any;

  constructor(
    private offerService: OfferService,
    private router: Router,
    private activatedRoute: ActivatedRoute) { }

  ngOnInit(): void {
    this.getAllOffers();
  }

  ngOnChanges(): void {
    this.getAllOffers();
  }

  // get all offers on observable
  getAllOffers(): void {
    this.offerService.getAll().subscribe(data => {
      this.offers = data;
    });
  }

  // to update the table of offers
  detectTrigger(event: Event): void {
    this.getAllOffers();
    console.log(this.offers);
  }

  selectOffer(id: number): void {
    this.router.navigate([id], {relativeTo: this.activatedRoute});
  }


  addOffer(): void{
    this.offerService.AddOffer();
  }

Answer 1

要持续从流中接收数据，您需要提供相同的引用。在服务getOffer 方法中，需要return this.offersSubject.asObservable(); 这是同一个流的read-only 部分。当您想要更新流时，您可以在原始流上调用 next。我已经创建了一些简单的 demo！ :)

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