title: AngularFire2 Getting Observable of type specific object
body: <p>I'm working on my first project using Angular and Firebase. Even thou everything works, I have a question about getting specific types of object. For example, I have a service that has a method called <code>getAllNews()</code>, but I want this return to be a type News (created by me, there is a NewsModel file) but when I set the type, I get this from TSLint:
  <code>[ts]
  Type 'Observable&lt;{}[]&gt;' is not assignable to type 'EventModel[]'.
  Property 'length' is missing in type 'Observable&lt;{}[]&gt;</code></p>
  
  <p>Can anybody shine a light here for me? Thank you so much!</p>
  
  <p>Here is my code:</p>
  
  <p><strong>newsService.ts</strong></p>
  
  <pre><code>import { Injectable } from '@angular/core';
  import { AngularFireDatabase, AngularFireList } from '@angular/fire/database';
  import { News } from '../news/news.model';
  @Injectable({
    providedIn: 'root'
  })
  export class NewsService {
  
    NODE = 'news/';
    news: AngularFireList&lt;News[]&gt;;
  
    constructor(private db: AngularFireDatabase) { }
  
    getAllNews() {
      const localNews = this.db.list(this.NODE);
      return localNews.valueChanges();
    }
  
    getNews(id: string) {
      return this.db.object(this.NODE + id);
    }
  }
  </code></pre>
  
  <p><strong>news.model.ts</strong></p>
  
  <pre><code>export class News {
      id: string;
      title: string;
      subtitle: string;
      article: string;
      picture: string;
  }
  </code></pre>
  
  <p><strong>news.component.ts</strong></p>
  
  <pre><code>import { News } from './news.model';
  import { Component, OnInit } from '@angular/core';
  import { NewsService } from '../services/news.service';
  import { Router } from '@angular/router';
  import { NavController } from '@ionic/angular';
  
  @Component({
    selector: 'app-news',
    templateUrl: './news.page.html',
    styleUrls: ['./news.page.scss'],
  })
  export class NewsPage implements OnInit {
  
    news: any;
  
    constructor(private newsService: NewsService, private router: Router, private navController: NavController) { }
  
    ngOnInit() {
      this.news = this.newsService.getAllNews();
    }
  
    go(id: string) {
      this.navController.navigateForward('news/' + id);
    }
  }
  </code></pre>
  
  <hr>