问不能在combineLatest上播放

EN

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';
import { combineLatest, distinctUntilChanged, map } from 'rxjs/operators';

export interface User {
  test: string;
}

export interface Item {
  test: string;
}

interface State {
  items: Item[];
  users: User[];
}

let _state: State = {
  items: [],
  users: [],
};

@Injectable()
export class Facade {
  private store = new BehaviorSubject<State>(_state);
  private state$ = this.store.asObservable();

  items$ = this.state$.pipe(map(state => state.items), distinctUntilChanged());
  emails$ = this.state$.pipe(map(state => state.users), distinctUntilChanged());

  constructor(private http: HttpClient) {
    combineLatest(this.items$, this.emails$).subscribe(
      ([items, users]) => {}
    );
  }
}