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

问题

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);
        }
      };
  }]);

回答1:

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);
});

来源：https://stackoverflow.com/questions/21721460/firebase-data-normalized-how-should-i-fetch-a-collection-based-on-this-structur

标签

angularjs

firebase

angularjs-service

angularfire