如何将Firebase连接到其他文件并显示所有文档？

Question

已连接Firebase，但无法在其他文件中使用它。需要知道如何访问并显示Firebase内容。

文件系统： src->应用程序->主页

app module.ts：

export class AppModule {}
var config = {
  apiKey: "AIzaSyBvJ0ZWfd2GcIpKgdcIaZKJ6ohLW_E7DOs",
  authDomain: "fir-storage-login.firebaseapp.com",
  databaseURL: "https://fir-storage-login.firebaseio.com",
  projectId: "firebase-storage-login",
  storageBucket: "firebase-storage-login.appspot.com",
  messagingSenderId: "803036592201"
};
var app = firebase.initializeApp(config);
var database = firebase.database(app);

home.page.html

<ion-content>
    <ion-searchbar (ionInput)="getStations($event)"></ion-searchbar>
        <ion-list>
          <ion-item *ngFor="let station of stations">
              {{ station }}
          </ion-item>
        </ion-list>
  </ion-content>

home.page.ts

import * as firebase from 'firebase/app';
import { AppModule } from '../app.module';

states: Array<any>;

initializeStates(){  
return firebase.database().ref('States').once('value').then(snapshot =`> 
snapshot.val());{
this.states }