Authservice vs AngularFirestone

[SimonIoa]

Hello i am using authservice to call my MySql database with PHP api and therefore my php functions for my Ionic 3 Angular 4 app.

This is how i call to get userData and it works fine

  import { AuthService } from "../../providers/auth-service";

  public authService: AuthService,
private loadingCtrl: LoadingController

 ) {
const data = JSON.parse(localStorage.getItem("userData"));
this.userDetails = data.userData;
this.userPostData.uid = this.userDetails.uid;
let loader = this.loadingCtrl.create({
    content: 'Please wait...'
});

I have another project that uses AngularFirestone

 import { AngularFirestore, AngularFirestoreDocument } from  'angularfire2/firestore';
  import { AngularFireAuth } from 'angularfire2/auth';
  import { Storage } from '@ionic/storage';

and calls the constructor like this

private users: AngularFirestoreDocument<{}>;

constructor(public navCtrl: NavController,
private afService: AngularFirestore,
private storage: Storage,
private loadingCtrl: LoadingController,
private afAuth: AngularFireAuth) {
this.uid = localStorage.getItem('uid');
this.users = this.afService.collection('users').doc(this.uid);
let loader = this.loadingCtrl.create({
  content: 'Please wait...'
});
loader.present();
this.users.valueChanges()
  .subscribe((res: any) => {
    this.canDoMessage = res.canDoMessage;
    loader.dismiss();
  }, error => {
    loader.dismiss();
  });
}

What i am asking how i call the users in my case? My authservice case

[SimonIoa]

Basically what i am asking is how to call the 'users' on AuthService
constructor( public authService: AuthService,,

like this on Firestone

constructor(private afService: AngularFirestore) { **this.users = afService.collection('users')**; }