如何使用Angular Firestore检索子集合？

npm install firebase @angular/fire

export const environment = {
  production: false,
  firebase: {
    apiKey: "YOUR_API_KEY",
    authDomain: "YOUR_AUTH_DOMAIN",
    projectId: "YOUR_PROJECT_ID",
    storageBucket: "YOUR_STORAGE_BUCKET",
    messagingSenderId: "YOUR_MESSAGING_SENDER_ID",
    appId: "YOUR_APP_ID"
  }
};

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AngularFireModule } from '@angular/fire';
import { AngularFirestoreModule } from '@angular/fire/firestore';
import { environment } from '../environments/environment';

@NgModule({
  imports: [
    BrowserModule,
    AngularFireModule.initializeApp(environment.firebase),
    AngularFirestoreModule
  ],
  declarations: [AppComponent],
  bootstrap: [AppComponent]
})
export class AppModule { }

import { Component } from '@angular/core';
import { AngularFirestore } from '@angular/fire/firestore';

@Component({
  selector: 'app-my-component',
  template: `
    <ul>
      <li *ngFor="let item of subCollectionItems$ | async">{{ item.name }}</li>
    </ul>
  `
})
export class MyComponent {
  subCollectionItems$: Observable<any[]>;

  constructor(private firestore: AngularFirestore) {
    const parentCollectionRef = this.firestore.collection('parentCollection');
    const parentDocRef = parentCollectionRef.doc('parentDoc');
    const subCollectionRef = parentDocRef.collection('subCollection');

    this.subCollectionItems$ = subCollectionRef.valueChanges();
  }
}