Protractor get element by model in repeater array

For example, in HTML page:

<tr ng-repeat="post in posts">
    <td ng-click="activePost(post)" class="title">{{post.title}}</td>
    <td><button class="btn btn-danger" ng-click="delete(post)">Delete</button></td>
  <td><input type="checkbox" ng-model="post.active" 
        id="{{post.id}}" /></td>
 </tr>

Then, I want something like:

element.all(by.repeater('post in posts')).then(function(posts) {
   var activePost = posts[0].element(by.model('active'));
   expect(activePost).toEqual(true);
});

This returns an unable to find element. I am basing this on this question and answer: Protractor find element inside a repeater