exemplo 4.4 – watch.html

	<!doctype html>
	<html ng-app="myApp">
	<body>
	  <div ng-controller="MyController">
	    <input type="text" ng-model="total" />
	    <button ng-click="increment()">Incrementar Total pelo Controller</button><br />
	    <hr />
	      <span>{{total}}</span>
	    <hr />
	    <b>$watch listener =</b> {{listenerMessage}}
	  </div>
	<script src="angular.min.js"></script>
	<script type="text/javascript">
	var app = angular.module('myApp', []);
	app.controller('MyController', [ '$scope', function($scope) {
		$scope.total = 0;
		
		$scope.listenerMessage = '';
		
		function totalChanged(newValue, oldValue) {
		  $scope.listenerMessage = 'Valor Antigo: ' + oldValue + ', Novo valor: ' + newValue;
		}
		
		// observa alterações de $scope.total
		$scope.$watch('total', totalChanged);
		
		$scope.increment = function(){
			$scope.total++;
		}
	}]);
	</script>
	</body>
	</html>