将异步获取的数据传递给指令 [英] Passing asynchronously obtained data to a directive
问题描述
我目前有一个 AngularJS controller，它基本上通过 $http.get() 调用异步获取一些 JSON，然后链接获取数据到某个范围变量.
controller 代码的恢复版本:
mapsControllers.controller('interactionsController', ['$http', function($http) {var ctrlModel = this;$http.get("data/interactionsPages.json").成功(功能(数据){ctrlModel.sidebar = {};ctrlModel.sidebar.pages = 数据；}).错误(函数(){...})；}]);然后，我有一个自定义 directive，它通过 HTML 元素接收相同的范围变量.
指令代码的恢复版本:
mapsDirectives.directive('sidebar', function() {返回 {限制:'E'，范围 : {页数:'@'},控制器:函数($scope){$scope.firstPage = 0;$scope.lastPage = $scope.pages.length - 1;$scope.activePage = 0;//...},链接:功能(范围){控制台日志(范围.页面)；},templateURL : 'sidebar.html'}});HTML 的恢复版本:
<div ng-controller='interactionsController asinteractionsCtrl'><mm-sidebar pages='{{interactionsCtrl.ctrlModel.sidebar.pages}}'></mm-侧边栏>问题是，由于 $http.get() 是异步的，指令被错误地初始化(例如:$scope.pages.length - 1 是未定义).
我找不到任何可以为我解决此问题的方法，尽管提供了一些似乎可以解决此问题的解决方案.也就是说，我试图观察变量，只在检测到变化后初始化变量，正如许多其他帖子中所建议的那样.为了测试，我使用了类似的东西:
//... 指令的 return{ }链接:函数(){scope.$watch('pages', function(pages){如果(页)控制台日志(页)；});}我已经测试过了，$watch 函数没有被多次调用(记录的值为 undefined)，我认为这意味着它没有检测到变量值.但是，我确认该值正在更改.
那么，这里有什么问题?
移动控制器中 sidebar 对象的声明并将范围绑定更改为 =.
mapsDirectives.controller("interactionsController", ["$http", "$timeout",功能($http，$超时){var ctrlModel = this;ctrlModel.sidebar = {页数:[]};/*$http.get("data/interactionsPages.json").成功(功能(数据){//ctrlModel.sidebar = {};ctrlModel.sidebar.pages = 数据；}).错误(函数(){})；*/$超时(功能(){//ctrlModel.sidebar = {};ctrlModel.sidebar.pages = ["一", "二"];}, 2000);}]);mapsDirectives.directive('mmSidebar', [function() {返回 {限制:'E'，范围: {页数:'='},控制器:函数(){}，链接:函数(范围，元素，属性，ctrl){scope.$watch("pages", function(val) {scope.firstPage = 0;scope.lastPage = scope.pages.length - 1;scope.activePage = 0;});},templateUrl: 'sidebar.html'};}]);然后匹配指令名称并去掉大括号.
</mm-侧边栏> 这是一个工作示例:http://plnkr.co/edit/VP79w4vL5xiifEWqAUGI
I currently have an AngularJS controller that is basically getting some JSON asynchronously through a $http.get() call, then linking the obtained data to some scope variable.
A resumed version of the controller code:
mapsControllers.controller('interactionsController', ['$http', function($http) {
var ctrlModel = this;
$http.get("data/interactionsPages.json").
success(function(data) {
ctrlModel.sidebar = {};
ctrlModel.sidebar.pages = data;
}).
error(function() {...});
}]);
Then, I have a custom directive which receives those same scope variables through a HTML element.
A resumed version of the directive code:
mapsDirectives.directive('sidebar', function() {
return {
restrict : 'E',
scope : {
pages : '@'
},
controller : function($scope) {
$scope.firstPage = 0;
$scope.lastPage = $scope.pages.length - 1;
$scope.activePage = 0;
//...
},
link : function(scope) {
console.log(scope.pages);
},
templateURL : 'sidebar.html'
}
});
A resumed version of the HTML:
<body>
<div ng-controller='interactionsController as interactionsCtrl'>
<mm-sidebar pages='{{interactionsCtrl.ctrlModel.sidebar.pages}}'>
</mm-sidebar>
</div>
</body>
The problem is, since the $http.get() is asynchronous, the directive is being badly initialised (e.g: $scope.pages.length - 1 is undefined).
I couldn't find anything that solved this problem for me, although there are some presented solutions that would seem to solve the case. Namely, I tried to watch the variables, only initialising the variables after detected changes, as suggested in many other posts. For testing, I used something like:
//... inside the directive's return{ }
link: function() {
scope.$watch('pages', function(pages){
if(pages)
console.log(pages);
});
}
I've tested it, and the $watch function wasn't called more than once (the logged value being undefined), which, I assume, means it isn't detecting the change in the variable value. However, I confirmed that the value was being changed.
So, what is the problem here?
Move the declaration for the sidebar object in the controller and change the scope binding to =.
mapsDirectives.controller("interactionsController", ["$http", "$timeout",
function($http, $timeout) {
var ctrlModel = this;
ctrlModel.sidebar = {
pages: []
};
/*
$http.get("data/interactionsPages.json").
success(function(data) {
//ctrlModel.sidebar = {};
ctrlModel.sidebar.pages = data;
}).
error(function() {});
*/
$timeout(function() {
//ctrlModel.sidebar = {};
ctrlModel.sidebar.pages = ["one", "two"];
}, 2000);
}
]);
mapsDirectives.directive('mmSidebar', [function() {
return {
restrict: 'E',
scope: {
pages: '='
},
controller: function() {},
link: function(scope, element, attrs, ctrl) {
scope.$watch("pages", function(val) {
scope.firstPage = 0;
scope.lastPage = scope.pages.length - 1;
scope.activePage = 0;
});
},
templateUrl: 'sidebar.html'
};
}]);
Then match the directive name and drop the braces.
<mm-sidebar pages='interactionsCtrl.sidebar.pages'>
</mm-sidebar>
Here's a working example: http://plnkr.co/edit/VP79w4vL5xiifEWqAUGI
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