AngularJS 工厂函数无法访问本地存储的缓存变量

AngularJS factory function cannot access a locally stored cache variable

本文关键字：存储 缓存 变量 访问 工厂 函数 AngularJS      更新时间：2023-09-26
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这一点上，我已经在这里呆了10多个小时。这对我来说没有意义。我迫切需要澄清我做错了什么。下面是一个简单的工厂函数，它对 JSON 文件进行 AJAX 调用。没有异步。数据问题和一切正常。我遇到的问题是我正在尝试保存返回的结果并稍后访问它。如果变量被填充，我就不必进行第二次 AJAX 调用，我可以简单地获取局部变量的内容。我意识到还有其他方法可以做到这一点，但我特别喜欢使用这种工厂方法。

storyDataAsFactory.$inject = ['$log', '$http', '$q'];
angular.module('ccsApp').factory('storyDataAsFactory', storyDataAsFactory);
function storyDataAsFactory($log, $http, $q) {
    var storiesCache = [];
    function getStories(url) {
        url = url || '';
        if (url !== '') {
            var deferred = $q.defer();
            alert('inside getStories, length of storiesCache = ' + storiesCache.length); // this is always zero! Why?
            //determine if ajax call has already occurred;
            //if so, data exists in cache as local var
            if (storiesCache.length !== 0) {
                $log.info('Returning stories from cache.');
                deferred.resolve(storiesCache);
                return deferred.promise;
            }
            $http({method:'GET', url:url})
                .success(function (data, status, headers, config) {
                    deferred.resolve(data);
                })
                .error(function (data, status, headers, config) {
                    deferred.reject(status);
                });
            return deferred.promise;
        } else {
            $log.error('(within storyDataAsFactory) Failed to retrieve stories: URL was undefined.');
        }
    }
    return {
        stories: storiesCache,
        getStories: function(url) {
            alert('inside return factory object, length of stories = ' + this.stories.length);
            //getStories returns a promise so that routeProvider
            //will instantiate the controller when resolved
            return getStories(url);
        }
    };
}

你需要使用一个承诺。我没有运行下面的代码，但这就是这个想法：

angular.module('ccsApp').service('storyDataAsFactory', storyDataAsService);
function storyDataAsService($log, $http, $q) {
    var storiesCache = [];
    function getStories(url) {
        url = url || '';
        if (url !== '') {
            alert('inside getStories, length of storiesCache = ' + storiesCache.length); // this is always zero! Why?
            if (storiesCache.length == 0) {
               return $http({method:'GET', url:url});
            } else {
                var deferred = $q.defer();
                deferred.resolve(storiesCache);
                return deferred.promise;
            }
        } else {
            $log.error('(within storyDataAsFactory) Failed to retrieve stories: URL was undefined.');
        }
    }
    return {
        getStories: function(url) {
            return getStories(url).then(function(stories) {
                // Do whatever
                return stories;
            });
        }
    };
}

storyDataAsService.getStories().then(function(stories) {
    $scope.stories = stories
})
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