使充当过滤器的功能

我是AngularJS的新手。我试图使该功能可以用作过滤器：

index.html

    <ul class="phones">
      <li ng-repeat="phone in phones | filter:isLong">
        {{phone.name}}
      </li>
    </ul>

controllers.js

phonecatApp.controller('PhoneListCtrl', function ($scope) {

  $scope.phones = [
    {'name': 'Nexus S',
     'snippet': 'Fast just got faster with Nexus S.'},
    {'name': 'Motorola XOOM™ with Wi-Fi',
     'snippet': 'The Next, Next Generation tablet.'},
    {'name': 'MOTOROLA XOOM™',
     'snippet': 'The Next, Next Generation tablet.'}
  ];

  $scope.islong = function(phone) {
    var n = phone.name.length;
    if ( n > 7) { return true } else { return false };
  }
});

杰斯宾

http://jsbin.com/huwam/1/edit

但这不起作用...请帮助我。谢谢你的好意。