Pre-populate children and grandchildren when a parent is created. The app has a set of bridge—the card game—Exercises, each Exercise consisting of 8 Hands, each Hand having an Answer for each Row within the Exercise's associated Situation.

pre-populating_children.coffee

App.ExercisesNewController = App.ObjectController.extend
  create: ->
    situation_id = $('#id_situation').val()
    situation = App.Situation.find(situation_id)
    @content.set 'situation', situation
    rows = situation.get('rows')
    
    @content.save().then =>
      for i in [1..8]
        hand = App.Hand.createRecord
          exercise: @content
          order: i
        hand.save().then (hand) =>
          rows.forEach (row) ->
            answer = App.Answer.createRecord
              row: row
              hand: hand
              min: ''
              mid: ''
              max: ''
            answer.save()
      @store.commit()
      @success "Exercise created!"
      @transitionToRoute 'exercises.edit', @content