parsley/app/models/recipe_ingredient.rb

class RecipeIngredient < ActiveRecord::Base

  belongs_to :ingredient
  belongs_to :recipe, inverse_of: :recipe_ingredients

  validates :sort_order, presence: true

  def name
    if self.ingredient_id.present?
      self.ingredient.name
    else
      super
    end
  end

  def display_name
    str = [quantity, units, name].delete_if { |i| i.blank? }.join(' ')
    str << ", #{preparation}" if preparation.present?
    str
  end

  def scale(factor, auto_unit = false)
    if factor.present? && self.quantity.present? && factor != '1'

      value_unit = UnitConversion.parse(self.quantity, self.units)
      value_unit = value_unit.scale(factor)

      if auto_unit
        value_unit = value_unit.auto_unit
      end

      self.quantity = value_unit.pretty_value
      self.units = value_unit.unit.to_s
    end
  end

end