Angular 15: Unexpected Change Detection Behavior with Nested Observables in Component
I've spent hours debugging this and I've been banging my head against this for hours..... I'm encountering a strange issue with change detection in my Angular 15 application when dealing with nested observables. I have a parent component that fetches a list of users, and for each user, I need to fetch their corresponding roles from another service. I am using `forkJoin` to combine these requests, but I noticed that the view isn't updating correctly when the data changes. Despite subscribing to the observable, the UI sometimes shows stale data. Here's a simplified version of my code: ```typescript import { Component, OnInit } from '@angular/core'; import { forkJoin, Observable } from 'rxjs'; import { map } from 'rxjs/operators'; import { UserService } from './user.service'; import { RoleService } from './role.service'; @Component({ selector: 'app-user-list', template: ` <div *ngFor="let user of users"> <p>{{ user.name }}</p> <p *ngIf="user.roles">Roles: {{ user.roles.join(', ') }}</p> </div> `, }) export class UserListComponent implements OnInit { users: any[] = []; constructor(private userService: UserService, private roleService: RoleService) { } ngOnInit() { this.userService.getUsers().pipe( switchMap(users => { const rolesRequests = users.map(user => this.roleService.getRoles(user.id)); return forkJoin(rolesRequests).pipe( map(roles => users.map((user, index) => ({ ...user, roles: roles[index] })))); }); }) ).subscribe(users => { this.users = users; console.log('Users with roles:', this.users); }, error => { console.error('Error fetching users or roles:', error); }); } } ``` I have tried using `ChangeDetectorRef.detectChanges()` after updating the users array, but it doesn't seem to solve the issue consistently. I also verified that the data returned from the services is correct, and I'm using `async` pipes elsewhere without issues. Is there something I'm missing in how Angular's change detection works with nested observables? Any insights or best practices would be very helpful! This is part of a larger application I'm building. Is there a better approach?