Get Error using this code.

import { Component } from '@angular/core'; import { IonicPage, NavController, NavParams } from 'ionic-angular'; import { AngularFireDatabase,AngularFireList } from 'angularfire2/database'; import { ShoppingItem } from '../../models/shopping-item/shopping-item.interface'; import { Subscription } from 'rxjs/Subscription'; import {AddShoppingPage} from '../../pages/add-shopping/add-shopping'; @Component({ selector: 'page-edit-shopping-item', templateUrl: 'edit-shopping-item.html', }) export class EditShoppingItemPage { shoppingItemRef$: any; shoppingItem = {} as ShoppingItem; shoppingItemSubscription: Subscription; constructor(public navCtrl: NavController, public navParams: NavParams, private database: AngularFireDatabase ) { const shoppingItemId = this.navParams.get('shoppingItemid'); console.log('shoppingItemId:', shoppingItemId); this.shoppingItemRef$ = this.database.object(shopping-list/${shoppingItemId}); this.shoppingItemRef$.subscribe(shoppingItem => this.shoppingItem = shoppingItem);

}

editShoppingItem(shoppingItem: ShoppingItem){
  this.shoppingItemRef$.update(shoppingItem);
  this.navCtrl.pop();
}

ionViewDidLoad() { console.log('ionViewDidLoad EditShoppingItemPage'); }

}

This is my code. And i get this error while i click on Edit button:

shindesharad71 / Ionic-Firebase-Shopping-List

Get Error using this code. #1