angular - fail to update array from service - angularjs

Question

I got a service that contain some contacts (name,phone). The controller has array that contain a reference to the array from the service so for every change on the array all gets updated.
Service:
app.service('ContactManagerService', function()
{
this.Contacts=[];
...
this.AddContact=function(Contact){...};
this.RemoveContact=function(Contact){...};
...
});
First question: Is this a good approach? Should every controller/directive need to have a direct reference to the original array from the service? I have read a lot about setting up some events from the service to the controllers when the array has been changed, but it sound stupid because the array on the controller will be change anyway (because its the same array) and the ng-repeat will be updated automatically.
Second problem: The service has a method that replace the array to new one:
this.ReplaceContacts=function(NewContacts)
{
this.Contacts=NewContacts;
});
The ng-repeat does not update because the controller still got the old reference to the old array. So a refresh need to be done.
I tried to replace the code to this one so the same array's reference wont change, but when the the code enter the foreach, this.Contacts array is undefined and the code stops. Why ?!
this.ReplaceContacts=function(NewContacts)
{
this.Contacts.splice(0, this.Contacts.length); //remove all contacts
NewContacts.forEach(function (contact, index)
{
this.Contacts.push(contact);//place the new ones
});
});
The controller code:
app.controller("myCtrl",
function ($scope,ContactManagerService)
{
$scope.Contacts = ContactManagerService.Contacts;
$scope.AddContact= function (Contact1) {
ContactManagerService.AddContact(Contact1);
}
$scope.RemoveContact = function (ContactID) {
ContactManagerService.RemoveContact(ContactID);
}
});
I hope everything is clear,
Thanks.

Answer 1

Because the callback function passed to forEach isn't bound to the service instance. So this, inside the callback, is not the service.
My advice: avoid this like the plague. It's an enormous source of bugs in JavaScript.
Use
var self = this;
at the top of the service, and use self instead of this everywhere.
Or bind the callback function to the service instance:
NewContacts.forEach(function (contact, index) {
...
}, this);

Answer 2

You can simply push elements to Contacts using Array.prototype.push()
The push() method adds one or more elements to the end of an array and returns the new length of the array.
this.ReplaceContacts=function(NewContacts){
this.Contacts.splice(0, this.Contacts.length); //remove all contacts
Array.prototype.push(this.Contacts, NewContacts);
});

Answer 3

As mentioned in previous anser, context of this in forEach loop is not what you think it is.
A simplification would be to use Array.prototype.concat():
var self = this;
self.ReplaceContacts = function (NewContacts) {
self.Contacts.splice(0, this.Contacts.length); //remove all contacts
self.Contacts.concat(NewContacts);
});