Angular EventEmitter 未在訂閱者中發出

Question

我有一個事件發射器，我想向父組件發射 object 但是事件發射器沒有在訂閱者 function 中發射

代碼

---

categories = [];

  @Output() filteredCategory = new EventEmitter<any>();
  @Output() maxiumPriceEmitter = new EventEmitter<any>();
  categorySub: Subscription;
  formatLabel(value: number) {
    return 'R' + value;
  }

  constructor(private shopService: ShopService) {}

  ngOnInit() {
    this.initCategories();
    this.filterCategories();
    this.updateCategories();
  }

filterCategories() {
    this.shopService.filterCategories.subscribe(
        (fCategory: string) => {
        this.categories.map(category => {
            category.checked = category.name === fCategory;
          });
        this.updateCategories();
        });
  }
  initCategories() {
    this.categories = [
      { name: 'dress', checked: true, displayName: 'Dresses' },
      { name: 'top', checked: true, displayName: 'Shirts' },
      { name: 'skirt', checked: true, displayName: 'Skirts/Pants' },
      { name: 'purse', checked: true, displayName: 'Purse' },
      { name: 'bag', checked: true, displayName: 'Bags' },
    ];

  }

  updateCategories() {
    const categories = this.categories
      .filter((category) => {
        return category.checked;
      });
    console.log(categories);
    this.filteredCategory.emit(categories);
  }

事件發射器在訂閱者之外發出很好的信號，但是當它在訂閱者中時它不起作用？

父模板代碼

<app-filter-bar
(maxiumPriceEmitter) = 'updatedMaxiumPrice($event)'
(filteredCategory) = 'updateCategories($event)'

></app-filter-bar>

我也沒有在控制台中看到任何錯誤

Answer 1

原因之一可能是this.shopService.filterCategories Observable/Subject 在您訂閱它之前發出值。 解決方法是將 observable 更改為 ReplaySubject/BehaviorSubject。