angularJS/ionic 无法读取未定义的属性“then”

Question

我正在将缓存添加到我的应用程序中，从缓存数据、使其过期和重新缓存一切正常。当我实现在没有连接的情况下再次将相同过期数据放入缓存的功能时，我收到此错误：Cannot read property 'then' of undefined

这是我的控制器的代码：

.controller('ItemsCtrl', function($scope, $http, DSCacheFactory) {

    //handle the catche to hold the items lits.
    self.itemsCache = DSCacheFactory.get("itemsCache");
    /*
    *Function to re-refresh the cach after expire
    *re-use the old cache if no internet connection available
    */
    self.itemsCache.setOptions({
        onExpire: function(key, value){
            getItems()
                .then(function(){
                console.log("Items Cache was automatically refreshed", new Date());
            }, function(){
                console.log("Errorgetting data put expired item back in the cache", new Date());
            });
        }
    });

    function getItems(){
        var cacheKey = "items",
            itemsData = self.itemsCache.get(cacheKey);
        if(itemsData){
            // if data in the cache dont make  HTTP calls.
            console.log("Found Data in cache", itemsData);
            //recive Data from the cache
            $scope.items = itemsData;
        }
        else{//if no data in the catch make HTTP calls.
            //HTTP request to get the items data.
            $http.get('services/data.json')
             .success(function(data){
                console.log("Recived data via HTTP");
                //caching the data recived from the http calls.
                self.itemsCache.put(cacheKey, data);
                $scope.items = data;
            });
        }//end of the else statment
    }
    getItems();
})

Answer 1

函数 getItems 没有返回任何东西 - 看起来你打算返回一个承诺，所以它应该如下所示。

当您在缓存中找到该项目时，您可以使用 $q.when 创建一个在参数不是 Promise 时已经解析的 Promise。

当你没有找到它时，你可以从 $http.get 中返回链式承诺。

.controller('ItemsCtrl', function($scope, $http, DSCacheFactory, $q) {

    //handle the cache to hold the items list.
    self.itemsCache = DSCacheFactory.get("itemsCache");
    /*
    *Function to re-refresh the cache after expire
    *re-use the old cache if no internet connection available
    */
    self.itemsCache.setOptions({
        onExpire: function(key, value){
            getItems()
                .then(function(itemsData){
                console.log("Items Cache was automatically refreshed", new Date());
            }, function(){
                console.log("Error getting data put expired item back in the cache", new Date());
            });
        }
    });

    function getItems(){
        var cacheKey = "items",
            itemsData = self.itemsCache.get(cacheKey);
        if(itemsData){
            // if data in the cache dont make  HTTP calls.
            console.log("Found Data in cache", itemsData);
            //receive Data from the cache
            $scope.items = itemsData;
            return $q.when(itemsData);
        }
        else{//if no data in the catch make HTTP calls.
            //HTTP request to get the items data.
            return $http.get('services/data.json')
             .success(function(data){
                console.log("Received data via HTTP");
                //caching the data received from the http calls.
                self.itemsCache.put(cacheKey, data);
                $scope.items = data;
                return data;
            });
        }//end of the else statement
    }
    getItems();
})

Answer 2

这没用，我只是不想破坏这个问题。

.controller('ItemsCtrl', function($scope, $http, $q, DSCacheFactory) {

        //handle the cache to hold the items lits.
        self.itemsCache = DSCacheFactory.get("itemsCache");
        /*
        *Function to re-refresh the cache after expire
        *re-use the old cache if no internet connection available
        */
        self.itemsCache.setOptions({
            onExpire: function(key, value){
                getItems()
                    .then(function(){
                    console.log("Items Cache was automatically refreshed", new Date());
                }, function(){
                    console.log("Errorgetting data put expired item back in the cache", new Date());
                });
            }
        });

        function getItems(){
            var deferred = $q.defer(),
                cacheKey = "items",
                itemsData = self.itemsCache.get(cacheKey);

            if(itemsData){
                // if data in the cache dont make  HTTP calls.
                console.log("Found Data in cache", itemsData);
                //receive Data from the cache
                $scope.items = itemsData;
                deferred.resolve(itemsData);
            }
            else{//if no data in the catch make HTTP calls.
                //HTTP request to get the items data.
                $http.get('services/data.json')
                 .success(function(data){
                    console.log("Received data via HTTP");
                    //caching the data received from the http calls.
                    self.itemsCache.put(cacheKey, data);
                    $scope.items = data;
                    deferred.resolve(data);
                });
            }//end of the else statement
        }
        getItems();
    })