fix: show an error message if there is an error

Author: soliyn

apps/rxjs/11-high-order-operator-bug/src/app/app.service.ts

@@ -1,6 +1,6 @@
 import { inject, Injectable } from '@angular/core';
-import { merge, Observable, of } from 'rxjs';
-import { LocalDBService, TopicType } from './localDB.service';
+import { forkJoin, map, Observable, of } from 'rxjs';
+import { Info, LocalDBService, TopicType } from './localDB.service';
 
 @Injectable({ providedIn: 'root' })
 export class AppService {
@@ -9,11 +9,16 @@ export class AppService {
  getAllInfo = this.dbService.infos;
 
  deleteOldTopics(type: TopicType): Observable<boolean> {
+ const deleteTopics = (infoByType: Info[]) => {
+ const results$ = infoByType.map((t) =>
+ this.dbService.deleteOneTopic(t.id),
+ );
+ return forkJoin(results$).pipe(
+ map((results) => results.every((value) => value === true)),
+ );
+ };
+
  const infoByType = this.dbService.searchByType(type);
- return infoByType.length > 0
- ? infoByType
- .map((t) => this.dbService.deleteOneTopic(t.id))
- .reduce((acc, curr) => merge(acc, curr), of(true))
- : of(true);
+ return infoByType.length > 0 ? deleteTopics(infoByType) : of(true);
  }
 }

apps/rxjs/11-high-order-operator-bug/src/app/localDB.service.ts

@@ -5,7 +5,7 @@ import { of } from 'rxjs';
 
 export type TopicType = 'food' | 'book' | 'sport';
 
-interface Info {
+export interface Info {
  id: number;
  topic: TopicType;
 }