gistfile1.js

PostsRoute = Ember.Route.extend

  model: (params) ->
    @store.find 'post',
      iteration: @modelFor('iteration').get('id')

  setupController: (controller, model) ->
    controller.set 'model',     model
    controller.set 'iteration', @modelFor('iteration')

`export default PostsRoute;`

gistfile2.coffee

# the model here is the iteration
PostsNewController = Ember.ObjectController.extend

  needs: ['posts']

  postsController: Ember.computed.alias('controllers.posts')

  newPostBody: ''

  actions:
    newPost: ->
      store   = @get('store')
      newPost = store.createRecord 'post',
        body: @get('newPostBody')
        iteration: @get('model')

      newPost.save().then (persistedRecord) =>
        @get('postsController.model').pushObject(newPost)

`export default PostsNewController;`