AngularJS TypeError:$resource不是函数

我有以下控制器,它以以下形式给我带来麻烦

TypeError:$resource不是函数

指向 var Activities = $resource('/api/activities');

app.controller('AddActivityCtrl',['$scope','$resource','$location','$rootScope',
    function($scope, $rootScope, $resource, $location){
        console.log($scope.user.email);
        //$scope.activity.user = $rootScope.user.email;
        $scope.save = function(){
            var Activities = $resource('/api/activities');
            $scope.activity.events = [];
            Activities.save($scope.activity, function(){
                $location.path('/')
            })
        }
    }
]);

它以前工作得很好,但我刚刚测试了这个功能,而自从上次测试以来,我所做的一些事情似乎已经破坏了它。这可能是什么原因?

以下来自app.js

var activities = require('./routes/activities');
app.use('/api/activities', activities);

在我的活动中。js我有

//API point for listing all existing activities
router.get('/', function(req, res){
    var collection = db.get('Activity');
    //collection.find({}, function(err, activities){
    collection.find({user:req.user.email}, function(err, activities){
        if (err) throw err;
        res.json(activities);
    });
});

...