work

app/models/recipe.rb

@@ -70,18 +70,19 @@ class Recipe < ApplicationRecord
     self
   end
 
+  def yields=(val)
+    @yields_list = nil
+    super
+  end
+
   def yields_list
-    if self.yields.present?
+    @yields_list ||= self.yields.to_s.split(',').concat(['1 recipe']).map { |y| y.strip }.select { |y| y.present? }.map do |y|
-      self.yields.split(',').map { |y| y.strip }.select { |y| y.present? }.map do |y|
       begin
         UnitConversion::parse(y)
       rescue UntConversion::UnparseableUnitError
         nil
       end
     end.compact
-    else
-      []
-    end
   end
 
   def tag_names
@@ -141,6 +142,14 @@ class Recipe < ApplicationRecord
   end
 
   def custom_units
+    arbitrary = self.yields_list.select { |y| !y.mass? && !y.volume }
+    mass = self.yields_list.select { |y| y.mass? }
+    volume = self.yields_list.select { |y| y.volume? }
+
+    primary_unit = mass.first || volume.first
+    
+    Hash[arbitrary.map { |y| [y.unit.unit, primary_unit] }]
+
     Hash[yields_list.select { |y| !y.mass? && !y.volume? && y.unit }.map { [y.unit.unit, y] }]
   end
 

app/models/recipe_ingredient.rb

@@ -127,7 +127,7 @@ class RecipeIngredient < ApplicationRecord
       unit = self.units.present? ? self.units.downcase : ''
       pair = self.ingredient.custom_units.detect do |u, e|
         if unit.empty?
-          ['each', 'ech', 'item', 'per'].include?(u.downcase)
+          ['each', 'ech', 'item', 'per', 'recipe'].include?(u.downcase)
         else
           [u.downcase, u.downcase.singularize, u.downcase.pluralize].any? { |uv| [unit, unit.singularize, unit.pluralize].include?(uv) }
         end
@@ -149,6 +149,12 @@ class RecipeIngredient < ApplicationRecord
     gram_unit.raw_value
   end
 
+  # Based on current quantity and units, return the value with with to multiply each nutrient to get the total amount
+  # supplied by this ingredient
+  def calculate_nutrition_ratio
+
+  end
+
   def as_value_unit
 
     custom_unit = self.get_custom_unit_equivalent

spec/models/recipe_spec.rb

@@ -1,6 +1,29 @@
 require 'rails_helper'
 
 RSpec.describe Recipe, type: :model do
+  describe '#yields_list' do
+    it 'always has "1 recipe" as a yield' do
+      r = create(:recipe, yields: '')
+      l = r.yields_list
+      expect(l.length).to eq 1
+      expect(l.first).to be_a UnitConversion::ValueUnit
+      expect(l.first.value.value).to eq 1
+      expect(l.first.unit.unit).to eq 'recipe'
+    end
+
+    it 'caches the list and resets it when yield is changed' do
+      r = create(:recipe, yields: '3 cups')
+      l1 = r.yields_list
+      l2 = r.yields_list
+      expect(l1.first).to equal(l2.first)
+
+      r.yields = '4 cups'
+      l2 = r.yields_list
+
+      expect(l1.first).not_to equal(l2.first)
+    end
+  end
+
   describe '#update_rating!' do
 
     it 'should set rating to nil with no ratings' do