如果您想避免$watch的暴政和开销，您总是可以使用老式的观察器模式。

在服务中:

factory('aService', function() {
  var observerCallbacks = [];

  //register an observer
  this.registerObserverCallback = function(callback){
    observerCallbacks.push(callback);
  };

  //call this when you know 'foo' has been changed
  var notifyObservers = function(){
    angular.forEach(observerCallbacks, function(callback){
      callback();
    });
  };

  //example of when you may want to notify observers
  this.foo = someNgResource.query().$then(function(){
    notifyObservers();
  });
});

在控制器中:

function FooCtrl($scope, aService){
  var updateFoo = function(){
    $scope.foo = aService.foo;
  };

  aService.registerObserverCallback(updateFoo);
  //service now in control of updating foo
};

没有手表或观察者回调(http://jsfiddle.net/zymotik/853wvv7s/):

JavaScript:

angular.module("Demo", [])
    .factory("DemoService", function($timeout) {

        function DemoService() {
            var self = this;
            self.name = "Demo Service";

            self.count = 0;

            self.counter = function(){
                self.count++;
                $timeout(self.counter, 1000);
            }

            self.addOneHundred = function(){
                self.count+=100;
            }

            self.counter();
        }

        return new DemoService();

    })
    .controller("DemoController", function($scope, DemoService) {

        $scope.service = DemoService;

        $scope.minusOneHundred = function() {
            DemoService.count -= 100;
        }

    });

HTML

<div ng-app="Demo" ng-controller="DemoController">
    <div>
        <h4>{{service.name}}</h4>
        <p>Count: {{service.count}}</p>
    </div>
</div>

这个JavaScript在我们从服务返回一个对象而不是一个值时工作。当一个JavaScript对象从服务返回时，Angular会向它的所有属性中添加手表。

还要注意，我使用'var self = this'，因为我需要在$timeout执行时保持对原始对象的引用，否则'this'将引用窗口对象。

当我面对一个非常相似的问题时，我观察了一个作用域中的函数，并让函数返回服务变量。我已经创建了一个js小提琴。您可以在下面找到代码。

    var myApp = angular.module("myApp",[]);

myApp.factory("randomService", function($timeout){
    var retValue = {};
    var data = 0;

    retValue.startService = function(){
        updateData();
    }

    retValue.getData = function(){
        return data;
    }

    function updateData(){
        $timeout(function(){
            data = Math.floor(Math.random() * 100);
            updateData()
        }, 500);
    }

    return retValue;
});

myApp.controller("myController", function($scope, randomService){
    $scope.data = 0;
    $scope.dataUpdated = 0;
    $scope.watchCalled = 0;
    randomService.startService();

    $scope.getRandomData = function(){
        return randomService.getData();    
    }

    $scope.$watch("getRandomData()", function(newValue, oldValue){
        if(oldValue != newValue){
            $scope.data = newValue;
            $scope.dataUpdated++;
        }
            $scope.watchCalled++;
    });
});

据我所知，你不需要做那么复杂的事情。您已经将foo从服务分配到作用域，并且由于foo是一个数组(反过来又是一个对象，它是通过引用分配的!)． 所以，你所需要做的就是这样:

function FooCtrl($scope, aService) {                                                                                                                              
  $scope.foo = aService.foo;

 }

如果这个Ctrl中的其他变量依赖于foo的变化，那么是的，你需要一个手表来观察foo并对该变量进行更改。但只要是简单的参考观看是不必要的。希望这能有所帮助。

// service:(这里没有什么特别的)

myApp.service('myService', function() {
  return { someVariable:'abc123' };
});

/ / ctrl:

myApp.controller('MyCtrl', function($scope, myService) {

  $scope.someVariable = myService.someVariable;

  // watch the service and update this ctrl...
  $scope.$watch(function(){
    return myService.someVariable;
  }, function(newValue){
    $scope.someVariable = newValue;
  });
});

有点丑，但我已经为切换添加了范围变量的注册到我的服务:

myApp.service('myService', function() {
    var self = this;
    self.value = false;
    self.c2 = function(){};
    self.callback = function(){
        self.value = !self.value; 
       self.c2();
    };

    self.on = function(){
        return self.value;
    };

    self.register = function(obj, key){ 
        self.c2 = function(){
            obj[key] = self.value; 
            obj.$apply();
        } 
    };

    return this;
});

然后在控制器中:

function MyCtrl($scope, myService) {
    $scope.name = 'Superhero';
    $scope.myVar = false;
    myService.register($scope, 'myVar');
}