我有一个simpe谷歌浏览器扩展程序。我正在使用书签,它存在于清单文件中。首先,我在控制器中使用Chrome书签api,并且效果很好。但是我决定将工厂用于清晰的代码和最佳实践。
我的index.html文件
<!DOCTYPE html>
<html lang="en" ng-app="BookmarksSharer" ng-csp>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
<title>bokmarks sharer</title>
<link rel="stylesheet" href="/css/main.css"/>
<script src="/javascript/jquery-2.1.1.min.js"></script>
<script src="/javascript/angular.min.js"></script>
<script src="/javascript/bookmark_sharer.js"></script>
<script src="/javascript/MainController.js"></script>
<script src="/javascript/BookmarkService.js"></script>
</head>
<body>
<div id="main_popup" ng-controller="MainController">
<p>Bookmarks</p>
<ul>
<li ng-repeat="bookmark_folder in bookmarks_folders" id="{{bookmark_folder.title}}">
{{bookmark_folder.title}}
<ul ng-repeat="bookmarks in bookmark_folder">
<li ng-repeat="bookmark in bookmarks | filter">{{bookmark.title}}</li>
</ul>
</li>
</ul>
</div>
</body>
</html>
bookmark_sharer.js很简单
var app = angular.module("BookmarksSharer", []);
MainController.js也非常简单。
app.controller('MainController',['$scope', 'bookmarkFactory', function($scope, bookmarkFactory){
$scope.boormarks_folders = bookmarkFactory.folders;
}]);
还有我的工厂
app.factory('bookmarkFactory', function () {
var bookmarks_folders;
function allBookmarksFolders(){
chrome.bookmarks.getTree(function(bookmarks_tree){
bookmarks_folders = bookmarks_tree[0].children;
});
return bookmarks_folders;
}
return {
folders: allBookmarksFolders()
};
});
为什么$ scope.bookmarks_folders是未定义的?
ExpertSystem您的代码也无法正常工作。简单的解决方案是
app.controller('MainController',['$scope', function($scope){
chrome.bookmarks.getTree(function(nodes){
$scope.bookmarks_folders = nodes[0].children;
$scope.$apply();
})
}]);
但是我想使用工厂或服务来组织我的代码。
chrome.bookmarks.getTree()
是异步的,因此到getAllBookmarks()
函数返回时,它bookmarks_folders
是未定义的。
您的服务会公开一个属性(folders
),该属性绑定到allBookmarksFolders()
alas的结果undefined
。
由于此操作是异步的,因此您的服务应返回一个Promise,因此控制器可以使用该Promise并在返回它时获取实际数据:
// The service
app.factory('bookmarkFactory', function ($q) {
function retrieveAllBookmarksFolders() {
var deferred = $q.defer();
chrome.bookmarks.getTree(function (bookmarks_tree) {
deferred.resolve(bookmarks_tree[0].children);
});
return deferred.promise;
}
return {
foldersPromise: retrieveAllBookmarksFolders()
};
});
// The controller
app.controller('MainController', function($scope, bookmarkFactory){
bookmarkFactory.foldersPromise.then(function (bookmarks_folders) {
$scope.boormarks_folders = bookmarks_folders;
});
});
主要问题来自以下事实:在您的实现中,您将返回绑定到bookmarks_folders
该点的值,然后在以后重新分配bookmarks_folders
以持有对另一个对象(bookmarks_tree[0].children
)的引用。
服务内部的事件流有点像这样:
bookmarks_folders
被声明(并初始化为未定义)。allBookmarksFolders()
执行并返回(仍未定义)bookmarks_folders
。folders
被分配了对当前所引用对象的引用bookmarks_folders
(即未定义)。getTree()
回调执行和受让人到bookmarks_folders
一个参照本发明的不同的对象(bookmarks_tree[0].children
)。那时,folders
对此一无所知,并继续引用先前的值(未定义)。另一种方法(由$resource
btw使用的一种方法)是不为分配新的引用bookmarks_folders
,而是修改已经引用的对象。
// The service
app.factory('bookmarkFactory', function () {
var bookmarks_folders = []; // initialize to an empty array
function allBookmarksFolders(){
chrome.bookmarks.getTree(function(bookmarks_tree){
// Here we need to modify the object (array)
// already referenced by `bookmarks_folders`
// Let's empty it first (just in case)
bookmarks_folders.splice(0, bookmarks_folders.length);
// Let's push the new data
bookmarks_tree[0].children.forEach(function (child) {
bookmarks_folders.push(child);
});
});
return bookmarks_folders;
}
return {
folders: allBookmarksFolders()
};
});
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