Firebase data normalized. How should I fetch a collection based on this structure?

Problem

I think I am getting close, I am able to print out the ID of books belonging to a user but have been trying unsuccessfully to fetch the list of books belonging to a user, from the firebase books reference.

I'm following loosely the tutorial here: http://www.thinkster.io/pick/eHPCs7s87O/angularjs-tutorial-learn-to-rapidly-build-real-time-web-apps-with-firebase#item-526e9330d90f99661f00046c

and also reading the documentation about denormalizing data here: https://www.firebase.com/blog/2013-04-12-denormalizing-is-normal.html

How should I go about it if I want to display the user in a page, followed by all its books?

firebase structure

FB
|
--user
| |
| --user1
|   |
|   --name: "test name"
|   --email: "test@test.com"
|   --books
|     |
|     "-JFZG3coHOAblHZ7XSjK": true
|     "-KJKJASDIUOPIWE9WEeJ": true
|     "-YtUTRGJLNL876F3SSwS": true
|
--books
  |
  --"-JFZG3coHOAblHZ7XSjK"
  | |
  | --title: "book title 1"
  | --ownerId: "user1"
  |
  --"-KJKJASDIUOPIWE9WEeJ"
  |  |
  |  --title: "book title 2"
  |  --ownerId: "user1" 
  |    
  --"-YtUTRGJLNL876F3SSwS"
  |  |
  |  --title: "book title 2"
  |  --ownerId: "user1" 

View

<div data-ng-controller="UsersController" data-ng-init="findOneUser()">
  <h2>Profile</h2>
  <img class="image_preview" data-ng-src="{{user.photoUrl}}">
  <p>Name: {{ user.name }}</p>
  <p>Name: {{ user.email }}</p>
  <a data-ng-href="#/users/{{ userId }}/edit">Edit</a>

  <h2>Coffee Blends</h2>

  <div data-ng-repeat="book in user.books">
    <p>---</p>
    <p>{{user.books}}</p>
  </div>
  <!--<div data-ng-controller="BooksController" data-init="">-->

  <!--</div>-->
</div>

Controller

'use strict';

angular.module('ccApp.controllers.users', ['ccApp.services.users'])
    .controller('UsersController', ['$scope', '$routeParams', '$location', 'angularFire', 'Users',
      function($scope, $routeParams, $location, angularFire, Users){

      $scope.user = {};
      $scope.userId = $routeParams.userId;

      $scope.findOneUser = function(userId){
        if (!!$scope.userId){
          angularFire(Users.find($routeParams.userId), $scope, 'user');
        }
      };

      $scope.updatePhotoUrl = function(url, user){
        $scope.fileUrl = url;
        console.log($scope.fileUrl[0].url);
        user.photoUrl = $scope.fileUrl[0].url;
      };

      $scope.findUsers = function(){
        $scope.users = Users.collection();
      };

      $scope.findWholesalers = function(){
        $scope.wholesalers = Users.collection();
      };

    }]);

Service

'use strict';

angular.module('ccApp.services.users', ['ccApp.services.firebaseRefs'])
  .factory('Users', ['angularFireCollection', 'FireRef',
    function(angularFireCollection, FireRef){
      return{
        collection: function(cb){
          return angularFireCollection(FireRef.users(), cb);
        }
      , find: function(userId){
          return FireRef.users().child('/'+userId);
        }
      };
  }]);
Problem courtesy of: Ryan W Kan

Solution

Begin by updating to angularFire 0.6. This looks 0.3.*ish. angularFire has been changed to $firebase and has a much more powerful and simplified interface.

Vanilla Firebase

I'll do this the hard way first as I think there is great value in understanding the underlying principle here. It's fairly complex, and I'll only cover the essentials. There are a lot of tiny edge cases to be handled as well:

angular.module('app', [])
    .controller('UsersController', function($scope, $firebase, $timeout, $routeParams){
      var userId = $routeParams.userId;
      $scope.user = $firebase(new Firebase('URL/user/'+userId));

      // or, for 3-way binding and automatic writes back to Firebase
      var userRef = $firebase(new Firebase('URL/users/'+userId)).$bind($scope. 'user');

      // grab this users' books using Firebase (the hard way)
      $scope.books = {};
      var booksRef = new Firebase('URL/books/');

      // fetch the user's book list dynamically because it may change in real-time
      var indexRef = new Firebase('URL/user/'+userId+'/books');

      // watch the index for add events
      indexRef.on('child_added', function(indexSnap) {
         // fetch the book and put it into our list
         var bookId = indexSnap.name();
         booksRef.child(bookId).on('value', function(bookSnap) {
            // trigger $digest/$apply so Angular syncs the DOM
            $timeout(function() {
               if( snap.val() === null ) {
                  // the book was deleted
                  delete $scope.books[bookId];
               }
               else {
                  $scope.books[bookId] = snap.val();
               }
            });
         });
      });

      // watch the index for remove events
      indexRef.on('child_removed', function(snap) {
         // trigger $digest/$apply so Angular updates the DOM
         $timeout(function(snap) {
            delete $scope.books[snap.name()];
         });
      });
});

Then the HTML (this will be the same for the other examples below):

<div data-ng-repeat="(bookId, book) in books">
   {{bookId}}: {{book.title}}
</div>

Some of the edge cases not fully covered here:

  • data is not sorted by priority ordering
  • when a record is deleted from index, should call off() on data paths
  • changes in ordering of the index won't change order of data records
  • value of the index is not stored anywhere for reference (if it matters)

FirebaseIndex

FirebaseIndex is a simple utility that takes an index like your book list and manages the code we just created above in a bit more sophisticated manner.

Unfortunately, FirebaseIndex doesn't support value events, so it can't be used with angularFire after 0.5.0 because of a change to angularFire's internal loading mechanisms. So it's not quite as short and sweet as it used to be.

angular.module('app', [])
.controller('UsersController', function($scope, $firebase, $timeout){
   var userId = $routeParams.userId;
   $scope.user = $firebase(new Firebase('URL/user/'+userId));

   var fb = new Firebase(URL);
   var index = new FirebaseIndex( fb.child('user/'+userId+'/books') );
   $scope.books = {};

   // almost magic
   index.on('child_added', function(snap) {
      $timeout(function() { $scope.books[snap.name()] = snap.val(); });
   });

   index.on('child_removed', function(snap) {
      $timeout(function() { delete $scope.books[snap.name()]; });
   });
});

Firebase.util.join

Firebase-util is a much more powerful and sophisticated library for normalizing paths. Because it returns an object that works just like a regular Firebase reference, it can also be used seamlessly with angularFire 0.5 and above.

angular.module('app', [])
.controller('UsersController', function($scope, $firebase){
   var userId = $routeParams.userId;
   $scope.user = $firebase(new Firebase('URL/user/'+userId)); 

   var fb = new Firebase(URL);
   var ref = new Firebase.util.intersection( fb.child('user/'+userId+'/books'), fb.child('books') );

   // magic!
   $scope.books = $firebase(ref);
});
Solution courtesy of: Kato

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