Ionic 2 Angularfire 2 retrieve collection from firebase - firebase

Question

I'm developing a mobile app using Ionic 2, Angularfire 2 and Firebase, but I'm stuck, this is my Firebase data structure:
I need to create a list from carrito, but at the same time I need to get the precio field and link it to another collection - precios, and get with the key value (as shown in the image above), the fields related (opcion & precio).
The code : list.ts
import { Component } from '#angular/core';
import { NavController, NavParams } from 'ionic-angular';
import {AngularFire, FirebaseListObservable} from 'angularfire2';
#Component({
selector: 'page-lista',
templateUrl: 'lista.html',
})
export class Lista {
public restaName:any;
serviceData: string;
carrito: FirebaseListObservable<any>;
precios: FirebaseListObservable<any>;
constructor(public navCtrl: NavController, public navParams:
NavParams, af: AngularFire, private shareService: ShareService) {
this.serviceData = shareService.getRestaName();
this.restaName = this.serviceData
this.carrito = af.database.list('/carrito', {
query: {
orderByChild: 'restaname',
equalTo: this.restaName
}
});
this.precios = af.database.list('/precios', {
query: {
orderByKey: true,
equalTo: this.precio ???? ---> HERE BEGIN MY DOUBTS
}
});
}
Here is part of lista.html
<ion-content padding>
<ion-list>
<ion-item *ngFor="let item of carrito | async ">
<p> {{item.prodname}} - {{item.cantidad}}</p>
</ion-item>
<ion-item *ngFor="let precio of precios | async "> ??? HOW CAN I GET THE FIELDS precio and opcion
<p>${{precio.precio}}</p>
</ion-item>
</ion-list>
</ion-content>
Any tips or comments will be appreciated !

Answer 1

You could use an Array of FirebaseObjectObservable instead of
precios: FirebaseListObservable<any>;
public precios :Array<FirebaseObjectObservable<any>>
this.carrito.subscribe(carrito => carrito.forEach(singleCarrito=>
precios.push(af.database.object('/precios/'+singleCarrito.precio))