RandomBook.book.service.ts

import { AngularFirestore, AngularFirestoreCollection } from '@angular/fire/firestore';
import { Injectable } from '@angular/core';
import { Book } from "../models/book.model";
import { Category } from '../models/category.model';
@Injectable({
  providedIn: 'root'
})
export class BookService {


  constructor(private fireStore: AngularFirestore) {
  }

  addBook(book: Book) {
    return this.fireStore.collection('Books').add({...book});
  }
 
  getBook(category: string) {
    return this.fireStore.collection('Books',ref=>ref.where('Categories','array-contains',category)).valueChanges();
  }

}