javascript - 错误 : [$compile:nonassign] Expression 'undefined' used with directive 'myFacebook' is non-assignable

Question

我正在用 angularjs 编写一个指令并得到上面提到的错误。我正在使用一本书中的代码。

.directive('myFacebook', [function(){
return {
    link: function(scope,element,attributes) {
        (function(d) {
                var js, id = 'facebook-jssdk',
                    ref = d.getElementsByTagName('script')[0];
                if (d.getElementById(id)) {
                    return;

                }
                js = d.createElement('script');
                js.id = id;
                js.async = true;
                js.src = "//connect.facebook.net/en_US/all.js";
                ref.parentNode.insertBefore(js, ref);
            }(document));
            // Initialize FB
            window.fbAsyncInit = function() {
                FB.init({

                    appId: 'xxxx', //birthday reminder
                    status: true, // check login status
                    cookie: true, // enable cookies to access the session
                    xfbml: false // parse XFBML
                });
                //Check FB Status
                FB.getLoginStatus(function(response) {
                     xxxx
                });
            };
        scope.username='';
    },
    scope: {
            permissions: '@',
            myFriends: '=friends'
        },
    controller: function($scope) {
        $scope.loadFriends = function() {
            FB.api('/me/friends?fields=birthday,name,picture', function(response) {
                    $scope.$apply(function() {
                        $scope.myFriends = response.data;
                    });
                });
        }
    },

    template:'Welcome {{username}}'
   }}])

我在

处遇到错误

 $scope.$apply(function() {
            $scope.myFriends = response.data;
 });

HTML代码

<div my-facebook></div>
<h1> My Friend's Birthday Reminder</h1>
<div ng-repeat="friend in myFriends">
     {{friend.name}}
</div>

Answer 1

我的解决方案在这里很难找到，但更容易实现。我不得不将其更改为等同于(请注意，问号使该属性成为可选属性。在 1.5 之前，这显然不是必需的)。

scope: {
    permissions: '@',
    myFriends: '=?friends'
}