Angular AJAX request not populating nested component state with async pipe - advanced patterns
I've searched everywhere and can't find a clear answer. I'm working on an Angular application (version 12) where I'm making an AJAX call using HttpClient to fetch user data. However, I'm working with a situation where the data is not correctly populating the state of a child component that uses the async pipe. My service method is returning an Observable, and I am subscribing to it in a parent component. Here's the relevant code for the parent component: ```typescript import { Component, OnInit } from '@angular/core'; import { UserService } from './user.service'; import { Observable } from 'rxjs'; @Component({ selector: 'app-user', template: `<app-user-detail [userData]='user$ | async'></app-user-detail>` }) export class UserComponent implements OnInit { user$: Observable<User>; constructor(private userService: UserService) {} ngOnInit() { this.user$ = this.userService.getUserData(); } } ``` In the child component, I have the following code: ```typescript import { Component, Input } from '@angular/core'; import { User } from './user.model'; @Component({ selector: 'app-user-detail', template: `<div>{{ userData?.name }}</div>` }) export class UserDetailComponent { @Input() userData: User; } ``` The question arises when the AJAX call completes and the data is supposed to be passed to the `app-user-detail` component. The `userData` input in the child component seems to be undefined when I check it in the template, even though the network request is successful and I can see the data in the console. Here's the console output: ``` GET http://localhost:3000/api/user 200 OK { "name": "John Doe", "age": 30 } ``` I've tried a few things to debug this scenario. First, I ensured that the `getUserData` method in my `UserService` looks like this: ```typescript import { Injectable } from '@angular/core'; import { HttpClient } from '@angular/common/http'; import { Observable } from 'rxjs'; import { User } from './user.model'; @Injectable({ providedIn: 'root' }) export class UserService { constructor(private http: HttpClient) {} getUserData(): Observable<User> { return this.http.get<User>('http://localhost:3000/api/user'); } } ``` Also, I checked that the `user$` observable is emitting values as expected, but it seems that when the child component tries to access `userData`, it hasn't been set yet. I’ve also tried implementing the `ngOnChanges` lifecycle hook in the child component, but that didn’t change the behavior. Has anyone encountered a similar scenario? What could be causing the input value to not update properly in the child component? Could this be related to change detection or the timing of the async pipe? Am I missing something obvious?