Angular @Effect监听指定Action类型的实现原理

@Effect()
  searchBookICanbeAnyName$: Observable<Action> = this.actions$.pipe(
    ofType(bookManage.SEARCH), // 监听bookManager.SEARCH action?
    debounceTime(300),
    mergeMap((action: bookManage.SearchAction) => {
      const nextSearch$ = this.actions$.pipe(ofType(bookManage.SEARCH), skip(1));
      return this.service.searchBooks(action.payload).pipe(
        takeUntil(nextSearch$),
        // If successful, dispatch success action with result
        map((data: BookResult) => ({type: bookManage.SEARCH_COMPLETE, payload: data.items})),
        // If request fails, dispatch failed action
        catchError(() => of({type: bookManage.SEARCH_COMPLETE, payload: []}))
      );
    })
  );