ActiveAdmin multi level has many configuration within Snacker

nutrition_data.rb

class NutritionData < ActiveRecord::Base
  attr_accessible :calories, :calories_from_fat, :header, :item_id, :serving, :nutrition_items_attributes

  validates :calories, :presence => true, :numericality => true
  validates :calories_from_fat, :presence => true, :numericality => true
  validates :header, :presence => true
  validates :serving, :presence => true

  belongs_to :item

  has_many :nutrition_items

  accepts_nested_attributes_for :nutrition_items, :allow_destroy => true
end

nutrition_item.rb

class NutritionItem < ActiveRecord::Base
  attr_accessible :nutrition_data_id, :title, :value, :child_nutrition_items_attributes

  validates :title, :presence => true
  validates :value, :presence => true

  belongs_to :nutrition_data
  belongs_to :parent, :class_name => 'NutritionItem'

  has_many :child_nutrition_items, :class_name => 'NutritionItem', :foreign_key => :parent_id
  
  accepts_nested_attributes_for :child_nutrition_items, :allow_destroy => true
end