title: $watch not working on variable from other controller?
body: <p>I have one controller which displays a checklist, and stores the selection in an array.</p>
  
  <p>My other controller runs an <code>$http.get</code> on the array from the first controller.</p>
  
  <p>How do I set a <code>$watch</code> so that whenever the array changes, a new HTTP GET request is sent?</p>
  
  <p>My attempt: <a href="http://plnkr.co/edit/EaCbnKrBQdEe4Nhppdfa" rel="nofollow">http://plnkr.co/edit/EaCbnKrBQdEe4Nhppdfa</a></p>
  
  <pre class="lang-js prettyprint-override"><code>// See plnkr for other controller + FooSelection factory + view
  function SimpleQueryResCtrl($scope, $http, FooSelection) {
      $scope.foo_list_selection = FooSelection;
  
      $scope.$watch('foo_list_selection', function (newValue, oldValue) {
          if (newValue !== oldValue)
              $http.get('/api/' + $scope.foo_list_selection).success(function (largeLoad) {
                  $scope.myData = largeLoad;
              });
      });
  }
  
  SimpleQueryResCtrl.$inject = ['$scope', '$http', 'FooSelection'];
  </code></pre>