當我嘗試從火庫，火庫獲取指定用戶時遇到問題。export class TaskService {  tasksCollection: AngularFirestoreCollection<Task>;  taskDoc: AngularFirestoreDocument<Task>;  tasks: Observable<Task[]>;  task: Observable<Task>;  constructor(private afs: AngularFirestore) {    this.tasksCollection = this.afs.collection('tasks', ref => ref.orderBy('title', 'asc'));  }  getTask(id: string): Observable<Task> {    this.taskDoc = this.afs.doc<Task>(`clients/${id}`);    this.task = this.taskDoc.snapshotChanges().pipe(map(action => {      if (action.payload.exists === false) {        return null;      } else {        const data = action.payload.data() as Task;        data.id = action.payload.id;        return data;      }    }));    return this.task;  }}這是我的文件Component.tsexport class TaskDetailsComponent implements OnInit {  id: string;  task: Task;  hasHours = false;  showHoursOnUpdate: false;  constructor(    private taskService: TaskService,    private router: Router,    private route: ActivatedRoute  ) { }  ngOnInit() {    // Get id from url    this.id = this.route.snapshot.params.id;    // Get client    this.taskService.getTask(this.id).subscribe(task => {      if (task != null) {        if (task.hours > 0) {          this.hasHours = true;        }      }      this.task = task;    });    console.log(this.id);    console.log(this.task);  }}id 的結果是好的。但對象（任務）的結果未定義。P.S我也有獲取所有用戶和添加新用戶的功能，所以如果這是相關的，請在評論中告訴我