I would suggest to define an itemController
on PostsController
which can take actions for individual post objects.
Then, in your template define the action (e.g. toggleBody) that toggles a property on the itemController. You can use this property to show or to hide the body of each post:
App.PostsController = Ember.ArrayController.extend
itemController: 'post'
App.PostController = Ember.ObjectController.extend
showBody: no
actions:
toggleBody: ->
@toggleProperty('showBody')
return false
<script type="text/x-handlebars" data-template-name="posts">
<ul>
{{#each}}
<li>{{title}} <span {{action toggleBody}} class='label'>Toggle</span>
{{#if showBody}}
<div>{{body}}</div>
{{/if}}
</li>
{{/each}}
</ul>
</script>
See also this jsFiddle for a working demo.