我有一个名为'DashboardState'的Angular工厂，我目前正在修改它以通过我的dashboardcontext Angular服务层处理API调用。
目前，我的所有widget数据都会持久保存到localStorage对象;但是，我现在正在进入一个新的c＃API层，它将布局小部件设置到永久存储器（即本例中的Sql Server数据库）。
我的主要问题是在promise函数的return this._getItemFromAPI($rootScope).then处返回load:时会发生什么。
在load:部分中，this是一个有效的对象，其中包含方法;但是，在.then部分内，我突然无法访问this.。
这对我来说是一个问题，因为我不能再打电话给this._handleSyncLoad了。正如您所看到的，我通过分配var handleSync = this._handleSyncLoad;尝试了一次黑客攻击，但是它没有解决范围问题。：
if (dashboardId != null && dashboardId != undefined) {
this.storage.setItem("defaultDashboardId", dashboardId);
var handleSync = this._handleSyncLoad;
return this._getItemFromAPI($rootScope).then(function (data) {
// save current current dashboard id for next time - 06/11/2015 BM:
return handleSync(data, true);
});
}
以下是'DashboardState'的完整列表：
angular.module('ui.dashboard')
.factory('DashboardState', ['$log', '$q', 'dashboardcontext', '$rootScope', function ($log, $q, dashboardcontext, $rootScope) {
function DashboardState(storage, id, hash, widgetDefinitions, stringify) {
this.storage = storage;
this.id = id;
this.hash = hash;
this.widgetDefinitions = widgetDefinitions;
this.stringify = stringify;
}
DashboardState.prototype = {
/**
* Takes array of widget instance objects, serializes, and saves state.
*
* @param {Array} widgets scope.widgets from dashboard directive
* @return {Boolean} true on success, false on failure
*/
save: function (widgets) {
// CODE OMITTED FOR SAVE FUNCTION
return true;
},
load: function (dashboardId) { // sent in from navigation-controller call
var useLocalStorage = false; // retrieve from localStorage or via API layer
var serialized;
if (useLocalStorage) { // retrieve dashboard layout from localStorage
// COME CODE OMITTED FOR BREVITY
serialized = this.storage.getItem(dashboardId);
}
}
else {
// FETCH DASHBOARD HERE !!
if (dashboardId != null && dashboardId != undefined) {
// *** "this" is available on the scope at this point ***
this.storage.setItem("defaultDashboardId", dashboardId);
var handleSync = this._handleSyncLoad;
return this._getItemFromAPI($rootScope).then(function (data) {
// *** "this" IS NO LONGER AVAILABLE ON THE SCOPE - i.e. I can no longer call this._handleSyncLoad from here ***
return handleSync(data, true);
});
}
else {
// revert to original line; see dashboardOptions to main-controller
serialized = this.storage.getItem(this.id);
}
}
if (serialized) {
// check for promise
if (angular.isObject(serialized)) { // && angular.isFunction(serialized.then)) { // modifed line 09/04/2015 BM:
return this._handleAsyncLoad(serialized);
}
// otherwise handle synchronous load
return this._handleSyncLoad(serialized);
} else {
return null;
}
},
_getItemFromAPI: function ($rootscope) {
// SERVER-SIDE API CALL TO PERSIST DASHBOARD TO STORAGE - 09/03/2015 BM:
var sid = $rootScope.rageSessionVars.sessionID;
var userid = $rootScope.rageSessionVars.userID;
var dashboardId = this.id;
return dashboardcontext.getDashboardImage(sid, userid, dashboardId).then(function (data) {
if (data.status == "FAIL") {
window.alert("Failed to retrieve dashboard. " + data.messages);
return false;
}
else {
return data;
}
});
},
_handleSyncLoad: function (serialized, isParsed) {
// **** MUST HANDLE THE isParsed PARAM; serialized object is alredy parsed ****
var deserialized, result = [];
if (!serialized) {
return null;
}
if (this == undefined) { // problem if coming from .then of this._getItemFromAPI in load: - 09/04/2015 BM:
deserialized = JSON.parse(serialized);
}
else {
if (this.stringify) {
try { // to deserialize the string
deserialized = JSON.parse(serialized);
} catch (e) {
// bad JSON, log a warning and return
$log.warn('Serialized dashboard state was malformed and could not be parsed: ', serialized);
return null;
}
}
else {
deserialized = serialized;
}
}
// check hash against current hash
if (deserialized.hash !== this.hash) {
$log.info('Serialized dashboard from storage was stale (old hash: ' + deserialized.hash + ', new hash: ' + this.hash + ')');
this.storage.removeItem(this.id);
return null;
}
// Cache widgets
var savedWidgetDefs = deserialized.widgets;
// instantiate widgets from stored data
for (var i = 0; i < savedWidgetDefs.length; i++) {
// deserialized object
var savedWidgetDef = savedWidgetDefs[i];
// widget definition to use
var widgetDefinition = this.widgetDefinitions.getByName(savedWidgetDef.name);
// check for no widget
if (!widgetDefinition) {
// no widget definition found, remove and return false
$log.warn('Widget with name "' + savedWidgetDef.name + '" was not found in given widget definition objects');
continue;
}
// check widget-specific storageHash
if (widgetDefinition.hasOwnProperty('storageHash') && widgetDefinition.storageHash !== savedWidgetDef.storageHash) {
// widget definition was found, but storageHash was stale, removing storage
$log.info('Widget Definition Object with name "' + savedWidgetDef.name + '" was found ' +
'but the storageHash property on the widget definition is different from that on the ' +
'serialized widget loaded from storage. hash from storage: "' + savedWidgetDef.storageHash + '"' +
', hash from WDO: "' + widgetDefinition.storageHash + '"');
continue;
}
// push instantiated widget to result array
result.push(savedWidgetDef);
}
return result;
},
_handleAsyncLoad: function (promise) {
var self = this;
var deferred = $q.defer();
promise.then(
// success
function (res) {
var result = self._handleSyncLoad(res);
if (result) {
deferred.resolve(result);
} else {
deferred.reject(result);
}
},
// failure
function (res) {
deferred.reject(res);
}
);
return deferred.promise;
}
};
return DashboardState;
}]);
非常感谢您的建议。
的问候， 鲍勃
答案 0 :(得分：1)
this总是引用当前函数，因此如果嵌套函数定义，则必须以某种方式解决它。
这是一个可以解决您问题的典型模式：
function someFunction() {
var that = this;
doSomething().then(function() {
// 'that' is your 'this'
});
}