AngularJS - Strange behaviour of promises in connection with notify() - promise

Question

As I want to implement a chat in AngularJS, I want to use the promise/deferred principle. My ChatService looks like the following:
factory('ChatService', ['$q', '$resource', function($q, $resource) {
var Service = {};
var connected = false;
var connection;
var chatResource = $resource('/guitars/chat/:action', {action: '#action'}, {
requestChatroomId: {
params: {
action: 'requestChatroomId'
},
method: 'GET'
},
sendMessage: {
params: {
action: 'sendMessage'
},
method: 'POST'
}
});
Service.connect = function(cb) {
var deferred = $q.defer();
chatResource.requestChatroomId(function(data) {
connection = new WebSocket('ws://127.0.0.1:8888/realtime/' + data.chatroomId);
connection.onerror = function (error) {
deferred.reject('Error: ' + error);
};
connection.onmessage = function (e) {
cb.call(this, e.data);
deferred.notify(e.data);
};
connected = true;
});
return deferred.promise;
};
Service.sendMessage = function(msg) {
if(!connected) {
return;
}
chatResource.sendMessage({message: msg});
}
return Service;
}])
My controller using the ChatService is:
app.controller('ChatCtrl', ['$scope', 'ChatService', function($scope, ChatService) {
$scope.chat = {};
$scope.chat.conversation = [];
var $messages = ChatService.connect(function(message) {
$scope.$apply(function() {
// #1 THIS FIRES EVERY TIME
$scope.chat.conversation.push(message);
});
});
$messages.then(function(message) {
console.log('Finishes - should never occur!')
}, function(error) {
console.log('An error occurred!')
}, function(message) {
// #2 THIS FIRES ONLY IF THERE IS AN INTERACTION WITH THE ANGULAR MODEL
console.log(message);
});
$scope.sendMessage = function(event) {
ChatService.sendMessage($scope.chat.message);
$scope.chat.message = '';
};
}]);
If something is pushed from the server, callback #1 is called, but callback #2 wont be called until there is some interaction with the angular-model, i.e. start writing something in the input-Box. What is the reason for that behaviour?

Answer 1

Okay the reason was, that AngularJS was not aware of a change. So I injected the $rootScope to my ChatService:
factory('ChatService', ['$q', '$resource', '$rootScope', function($q, $resource, $rootScope) {
and in connection.onmessage I called $apply() on $rootScope:
connection.onmessage = function (e) {
deferred.notify(e.data);
$rootScope.$apply();
};