为什么我的自定义角度滤镜不起作用？ （火力）

Question

我正在尝试为我的Ionic + Firebase应用做一个自定义角度过滤器。 我的观点是在＆＃34;聊天＆＃34;中重复使用firebase的用户标签。我想过滤它，所以它只显示已经与之交谈过的用户。 我试图在视图中调用filter，它返回错误：TypeError: Cannot read property 'length' of undefined。当我在控制器中调用它时，它显示空白页面，没有错误。我已经被困在这里很长一段时间了。

查看：

<ion-view view-title="Chats">
  <ion-content> 
     <ion-list >
      <ion-item  class="item-remove-animate item item-thumbnail-left" ng-repeat="user in users | chatfilter" type="item-text-wrap" href="#/tab/chats/{{ownId}}&ID={{user.id}}" id = "chatlist" >
        <img src="{{user.profilepic}}">
        <h2 id="nameId" ng-model = "nameid"> {{user.name}} <i class="icon ion-chevron-right icon-accessory"></i></h2>
      </ion-item>
    </ion-list>
  </ion-content>
</ion-view>

过滤器：

  .filter("chatfilter", function (Auth, $firebaseArray){
  return function(items){
    var filteredUsers = []; //I want to push users I've talked to here
    Auth.$onAuth(function(authData) {
        var ownid = authData.uid;  

        var messages = new Firebase("https://newbuddy.firebaseio.com/messages");
        var i = items.length;
        var latestSnapshot = null;
        var filtered = []; 
        // RegExp will check all messeges references, math those with logged in user's id, and push them to filtered.  
        messages.on('child_added', function(snap) { 
          latestSnapshot = snap.key(); 

          var patt = new RegExp(ownid.toString()); 
          var res = patt.test(latestSnapshot);
          if (res == true) {
            var receiver = latestSnapshot.replace(patt, "");
            filtered.push(receiver);
          }

          // loop will test ids from filtered against all users and push mathes into filtratedUsers.
          for (var j = 0; j < i; j++){

                if (filtered.indexOf(items[j].id) != -1) {
                  filteredUsers.push(items[j].id);
                } 
          }
    })
      return filteredUsers;
  });

 };
})