Angular + SignalR wait for promise - angularjs

Question

I have list of users for chat purpose, something like on facebook where i got all users from my database using ngResource. When user is offline i got red marker close to his name and when is online i use green marker.
What i want to archieve is that when user sign in, my red marker will turn into green. When user login into my app, my Hub method OnConnected() gets fired and call my client side code
Hub method when user sign in.
#region Connect
public override Task OnConnected()
{
var userDetails = new ApplicationUser
{
ConnectionId = Context.ConnectionId,
UserName = Context.Request.GetHttpContext().User.Identity.Name,
Id = HttpContext.Current.User.Identity.GetUserId(),
};
if (onlineUsers.Count(x => x.ConnectionId == userDetails.ConnectionId) == 0)
{
onlineUsers.Add(new ApplicationUser {
ConnectionId = Context.ConnectionId,
UserName = userDetails.UserName,
Id = userDetails.Id,
});
Clients.All.newOnlineUser(userDetails);
Clients.Caller.getOnlineUsers(onlineUsers);
}
return base.OnConnected();
}
#endregion
Client side code in my controller
$scope.online_users = UserService.getChatUsers();
PrivateChatService.addOnlineUser(function (user) {
angular.forEach($scope.online_users, function (value, key) {
if (user.UserId == value.Id) {
value.Active = true;
}
});
console.log("newOnlineUser finished");
});
Problem is with forEach method in my client side code. In that time when my signalR hub fires my method ".addOnlineUser" my $scope.online_users is not resolved so i only have promise but not data so i cant iterate through that array to change user status from offline to online. Is something how i can wait for promise to be resolved?
Update:
I had something like this but this is not definitely good aproach since i hit all the time my database to get users.`
PrivateChatService.addOnlineUser(function (user) {
var dataPromise = UserService.getChatUsers(function(response){
$scope.online_users = response;
angular.forEach(dataPromise, function (value, key) {
if (user.UserId == value.Id) {
value.Active = true;
}
});
});
console.log("newOnlineUser finished");
});