Reading child of an automated unique ID in a nested ng-repeat - angularjs

Question

How do I get data of a child of an automated unique ID in a nested ng-repeat, if the ID is not in the first level?
My firebase data set is structured as such (note: I do not know the amount or values of users, dates or unique IDs in that data set):
John:[
10-12-2015: {
"-JcFXid1A2G8EM7A_kwc": {
"description" : "hi",
"timestamp": "1449751857810"},
"-JcFZP5FNtL4Yj6nja_7": {
"description" : "this",
"timestamp": "144975185345"},
},
11-12-2015: {
"-JcFtGoZL7J-CCIjTYcL": {
"description" : "is",
"timestamp": "14497518513715"},
"-JcFXid1A2G8EM7A_kwc": {
"description" : "me",
"timestamp": "1449751846956"},
},
]
Thomas: [ ... ]
My HTML code is:
<ion-list>
<ul class="list">
<li ng-repeat="day in list">
<ion-item class="item-divider">{{day.$id}}</ion-item>
// That works as my output is "10-12-2015, etc"
<li ng-repeat="key in day">
// This does not work
<ion-item>{{key.description}}</ion-item>
</li>
</li>
</ul>
</ion-list>
I am new to Firebase and Angular so my apologies if I am missing something obvious. I also understand that Firebase recommends flat hierarchies, but sorting it by user and date is important for data analysis I need to do. But I would be open to suggestions.
FYI - My controller looks like this:
.controller('summaryCtrl', ['$scope','$state','$firebase','$firebaseArray','SessionData', '$ionicPopup', function($scope,$state,$firebase,$firebaseArray,SessionData,$ionicPopup){
var firebaseObj = new Firebase("https://id.firebaseio.com/" + userid);
var fbArray = $firebaseArray(firebaseObj);
fbArray.$loaded()
.then(function(){
$scope.list = fbArray;
})
}])
Thanks.

Answer 1

You don't need to use .$loaded(), the $firebaseArray will take care of triggering $digest when the data is loaded. The .$loaded() promise is useful for resolving in routes.
In your case though you need to go down into the day key to create the array. Try a data structure like below:
{
"userMessages": {
"$uid": {
"$message_id": {
"timestamp": 1450048003760 // use a timestamp
}
}
}
}
This way you can get messages per user by: /userMessages/$uid/. Then using a query you can get them by date.
You can create factory to simplify this.
Don't mind the code structure below, it uses the Angular Styleguide.
angular.module('app', ['firebase'])
.constant('FirebaseUrl', '<my-firebase-app>')
.service('rootRef', ['FirebaseUrl', Firebase])
.factory('messages', Messages)
.controller('SummaryCtrl', SummaryCtrl);
function Messages(rootRef, $firebaseArray) {
return function Messages(userid, date) {
// turn the date into a timestamp
var timestamp = date.getTime();
var messagesRef = rootRef.child('userMessages').child(userid);
// query for messages on that day
var query = messagesRef.orderByChild('timestamp').endAt(timestamp);
return $firebaseArray(query);
};
}
function SummaryCtrl($scope, messages, rootRef) {
var user = rootRef.getUser()
var today = new Date();
$scope.messages = messages(user.uid, today);
}