service.ts

import { Injectable } from '@angular/core';
import { AngularFire, FirebaseListObservable } from 'angularfire2';
import 'rxjs/add/operator/map';
import { Business } from '../Business';
import { Category } from '../Category';

@Injectable()

export class FirebaseService {


    businesses: FirebaseListObservable<Business[]>;
    categories: FirebaseListObservable<Category[]>;


    constructor(private _af: AngularFire){

    }

    getBusinesses(category:string = null){
      if (category !== null) {
        this.businesses = this._af.database.list('/businesses', {
          query: {
            orderByChild: 'category',
            equalTo: category
          }
        }) as FirebaseListObservable<Business[]>;
      } else {
        this.businesses = this._af.database.list('/businesses') as FirebaseListObservable<Business[]>;
      }
      
      return this.businesses;
    }

    getCategories(){
      this.categories = this._af.database.list('/categories') as FirebaseListObservable<Category[]>;
      return this.categories;
    }

  addBusiness(newBusiness){
        return this.businesses.push(newBusiness);
    }

  updateBusiness(key, updBusiness){
    this.businesses.update(key, updBusiness);
  }

  deleteBusiness(key){
    this.businesses.remove(key);
  }

}