Querying Denormalized Data in AngularFire 0.82: Best Practices and Strategies

I have a question that is related to querying denormalized data with AngularFire. I am looking for a solution specifically using AngularFire (current version 0.82). Here is an example of the data structure I am working with:

{
  "users": {
    "user1": {
      "name": "Alice",
      "lists": {
        "list1": "true"
      }
    },
    "user2": {
      "name": "Bob",
      "lists": {
        "list2": "true"
      }
    }
  },
  "lists": {
    "list1": {
      "title": "Example"
    },
    "list2": {
      "title": "Example2"
    }
  }
}

In another notation, to retrieve all lists of a user we need to access:

users/$userID/lists/$listID

The content of the lists can be found at:

lists/$listID

My goal is to access the content of a specific user's lists without manually iterating over each $ListID.

A more advanced response could provide code that encapsulates this access in an extended service for AngularFire, similar to the example under "Creating AngularFire Services" in the AngularFire documentation.

Answer №1

To effectively address the issue at hand, it is important to first understand the specific use case that needs resolution rather than solely focusing on a predetermined solution. Oftentimes, there are simpler and more efficient approaches to tackling the problem at hand (refer to What is the XY problem? for more insights).

While AngularFire does not have native support for handling nested lists of lists, creating a list of individual elements may prove to be a more straightforward option compared to managing multiple referenced lists within a list.

Firebase.util

A tool known as Firebase.util can aid in denormalization processes and is compatible with AngularFire. The upcoming V2 update of this tool is set for release within the next month or two:

var fbRef = new Firebase(URL);
var indexRef = fbRef.child('users/' + userId + '/lists');
var dataRef = fbRef.child('lists');
var joinedRef = Firebase.util.intersection(indexRef, dataRef);

var lists = $firebase( joinedRef ).$asArray();

Angular only

An Angular-exclusive approach involves manually loading the lists and utilizing AngularFire for managing individual lists:

app.factory('NestedList', function($firebase, $timeout) {
   return function(indexRef, dataRef) {
      var hashOfLists = {};
      indexRef.on('child_added', function(snap) {
         var key = snap.key();
         var list = $firebase( dataRef.child(key).$asArray();
         hashOfLists[key] = list;
      });
      indexRef.on('child_removed', function(snap) {
         $timeout(function() {
            delete hashOfLists[snap.key()];
         });
      });
      return hashOfLists;
   }
});

Please note that the example above utilizes snap.key(), which applies specifically to version 2.x of the SDK that was recently released. Prior versions should use snap.name()

To delve into more advanced functionalities and develop custom directives or services, refer to the discussion provided in this question and answer thread. Despite initial appearances, this resource offers comprehensive insights on transforming any Firebase dataset into a proprietary structure.

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