Model Service

modelservice.js

angular.module("test").service("Greeting", function() {
  this.greet = null;
  
  this.greetTo = function(name) {
    this.greet = "Hello " + name;
  }
});

angular.module("test").controller("TestCtrl", function(Greeting) {
  $scope.greeting = Greeting;
  
  $scope.$watch("greeting", function(){
    // The model has changed. Do something
  });
  
  $scope.greeting.greetTo("Gonto");
});