import { Component , OnInit } from '@angular/core' ; import { Observable } from 'rxjs' ; import { traceUntilFirst } from '@angular/fire/performance' ; import { Database , objectVal , ref } from '@angular/fire/database' ; @ Component ( { selector : 'app-database' , template : `
    <p>
      Database!
      <code>{{ testObjectValue$ | async | json }}</code>
    </p>
  ` , styles : [ ] } ) export class DatabaseComponent implements OnInit { public readonly testObjectValue$ : Observable < any > ; constructor ( database ) { const doc = ref ( database , 'test' ) ; this . testObjectValue$ = objectVal ( doc ) . pipe ( traceUntilFirst ( 'database' ) ) ; } ngOnInit ( ) { } }