如何访问子集合并将其作为 Observable 返回？

Question

如果我手动添加collectionRef，我就可以访问子集合。我尝试在构造函数之外使用 CollectionReference，但收到错误消息，指出类型“UnitlogService”上不存在属性“collectionRef”。我看到的唯一方法是如何在构造函数之前使用 getTasks 或在构造函数之外使用 CollectionReference 。有关子集合的任何帮助或 AngularFire 参考文档都会非常有帮助。

服务文件ts

import { collection, CollectionReference, Firestore }from'@angular/fire/firestore';

export class UnitlogService {
  private collectionRef: CollectionReference;

  constructor( private firestore: Firestore, private auth: Auth, private storage: Storage ) {

    // const id inserted manually
    // would like to use id form getTasks(id) which connects the page with this service
    const id = 'LvuYX0jreCB1sL5IORCM'

     this.collectionRef = collection(this.firestore, `tasks/${id}/unit-logs-sub-collection`);
     onAuthStateChanged(this.auth, (user) => {
       if (user) {
         const tasksQuery = query( this.collectionRef);
         const collectionSub = collectionData(tasksQuery, {
           idField: 'id',
        }) as Observable<Task[]>;
          this.tasksSub = collectionSub.subscribe((tasks) => {
          this.tasks.next(tasks);
        });
      } else {
      this.tasks.next([]);
      this.tasks.unsubscribe();
    }
  });
}

getTasks(id: any) {
  console.log("id",id)
  return this.tasks.asObservable() 
} 

Answer 1

如果您是 AngularFire 用户，则构造函数实际上无法修改。作为解决方法，我跳过了 CollectionReference 并在构造函数之外使用以下代码来查询子集合并将其作为 Observable 返回以在其他页面上使用

服务

import { collection, CollectionReference, Firestore }from'@angular/fire/firestore';

getSubCollection(id: any) {
  // id of collection "task" is passed form the page using the service
  const col = collection(this.firestore, `tasks/${id}/unit-logs-sub-collection`);
  // const col is the link to the sub collection
  const tasksQuery = query( col );
  const collectionSub = collectionData(tasksQuery, { idField: 'id',}) as Observable<Task[]>;
  
  this.tasksSub = collectionSub.subscribe((tasks) => { this.tasks.next(tasks); console.log("this.tasks",this.tasks);});
  // this.tasksSub is a BehaviorSubject
  return this.tasks.asObservable();
  // returns a Observable {source: BehaviorSubject}
}