Firebase/Angularfire: accessing static values of observables - firebase

Question

Assume I have a Firebase object with names for some IDs:
people: {
key1: {name: "Bob"},
key2: {name: "Sally"},
...
}
I create an AngularListObservable:
this.people$ = this.angularFireDatabase.list('people');
and feed this into the template as
<span *ngFor="let person of people$ | async">Hello {{person.key}}</span>
Now assume I want to create a new element in people, but base its name on the current number of keys. This requires me to somehow access a static version of people to count its elements. I have found the following three approaches:
One: maintain a current static value via a subscription in ngOnInit:
private currentPeople;
ngOnInit() {
this.people$.subscribe(people => this.currentPeople = people);
}
Then
public create() {
this.people.push({name: "person " + (this.currentPeople.length + 1)});
}
However, this requires me to keep track of the subscription and unsubscribe in ngOnDestroy.
Two: use take on the observable:
public create() {
this.people$.take(1).subscribe(people =>
this.people.push({name: "person " + (people.length + 1)});
);
}
But will this work reliably in getting the current value of the observable?
Three: back off into Angular database itself, entering the world of References and Snapshots, and do
public create() {
this.people$.$ref.once("value").then(peopleSnapshot =>
this.people.push({name: "person " + (peopleSnapshot.numChildren() + 1)});
}
Are any of three approaches considered best practices, or what other pluses and minuses do they have?

Answer 1

For static vars you can use an src/environments/environment.ts folder to hold static information in json format and access them using environment.myvar
In your app.modules.ts you would put
imports: [ AngularFireModule.initializeApp(environment.firebase),
import { environment } from '../environments/environment';