title: AngularFireList, property valueChanges() show the error Property 'query' is missing in type 'Observable<{}[]>
body: <p>I'm having a hard time to figure out this error. Here is my code that I'm building in to make a AuthGuard service:</p>
  
  <pre><code>user.service.ts:
  
  import { Injectable } from '@angular/core';
  
  import { AngularFireDatabase, AngularFireList } from 'angularfire2/database';
  
  import {AppUser} from './models/app.user';
  import * as firebase from 'firebase';
  
  @Injectable({
    providedIn: 'root'
  })
  export class UserService {
  
    constructor(private db: AngularFireDatabase) { }
  
    save(user: firebase.User) {
      this.db.object('/users/' + user.uid).update({
        name: user.displayName,
        email: user.email
      });
    }
  
    get(uid: string): AngularFireList&lt;AppUser&gt; {
      return this.db.list('/users/' + uid).valueChanges();
    }
  }
  </code></pre>
  
  <p>The property <code>.valueChanges()</code> shows me the error:</p>
  
  <p>:>Property 'query' is missing in type 'Observable&lt;{}[]></p>
  
  <p>I'm also having issues to get the uid:</p>
  
  <pre><code>in AuthGuardService.ts:
  
  import { Injectable } from '@angular/core';
  import { Observable } from 'rxjs/observable';
  import 'rxjs/add/operator/switchMap';
  import 'rxjs/operator/map';
  import { UserService } from './user.service';
  import { CanActivate } from '@angular/router';
  import { AuthService } from './auth.service';
  
  
  
  @Injectable({
    providedIn: 'root'
  })
  export class AdminAuthGuard implements CanActivate {
  
    constructor(private auth: AuthService, private userService: UserService) { }
  
    canActivate (): Observable&lt;boolean&gt; {
      return this.auth.user$
        .switchMap(user =&gt; this.userService.get(user.uid).valueChanges())
        .map (appUser =&gt; appUser.isAdmin);
    }
  }
  </code></pre>
  
  <p>The error is:</p>
  
  <blockquote>
    <p>message": "Property 'isAdmin' does not exist on type 'AppUser[]'."</p>
  </blockquote>
  
  <p>app.user.ts:</p>
  
  <pre><code>export interface AppUser {
      name: string;
      email: string;
      isAdmin: boolean;
  }
  </code></pre>
  
  <p>Can anyone help me to identify how to fix this? Thank you!</p>