clientDataService.clientDataObject是不是你的控制器范围的一部分，所以你不能观看该对象上的变化。
您需要注入$ rootScope到您的服务，然后将更改广播到控制器的作用域。

clientDataService.clientDataObject is not part of your controller's scope, so you can't watch for changes on that object. You need to inject the $rootScope into your service then broadcast the changes to the controllers scopes.

app.factory('clientDataService', function ($rootScope, $http) {
    var clientDataObject = {};
    var cdsService = {
        fetch: function (cid) {
            var promise = $http.get('/clients/stats/' + cid + '/').then(function (response) {
                // The then function here is an opportunity to modify the response
                console.log(response);
                // The return value gets picked up by the then in the controller.
                clientDataObject = {'data': response.data, 'currentClientID': cid};
                $rootScope.$broadcast('UPDATE_CLIENT_DATA', clientDataObject);
                return clientDataObject;
            });
            // Return the promise to the controller
            return promise;
        }
    };
    return cdsService;
});

然后在控制器，你可以听使用的变化：

Then in the controller you can listen for the change using:

$scope.$on('UPDATE_CLIENT_DATA', function ( event, clientDataObject ) { });