Add Quantity to a Recipe habtm Ingredients Relation

Question

I wanted to build a basic cookbook. With a Recipes habtm Ingredients Relation.

My first attempt was like this.

class Recipe < ActiveRecord::Base
  # title, description
  has_many :recipe_ingredients
end

class Ingredient < ActiveRecord::Base
  # name, unit
  has_many :recipe_ingredients
  has_many :recipes, :through => :recipe_ingredients
end

class RecipeIngredient < ActiveRecord::Base
  belongs_to :recipe
  belongs_to :ingredient
  attr_accessible :amount
end

And created the Relation by Hand

RecipeIngredient.create(:recipe_id => 1, :ingredient_id => 2, :amount => 100)

recipe.recipe_ingredients.amout
recipe.recipe_ingredients.ingredient.unit
recipe.recipe_ingredients.ingredient.name

This feels ugly. But I don't know any other solution.

Answer 1

Looks fine to me, as a schema/approach. I think it might just feel ugly because your choice of class name leads you to type "recipe.recipe_ingredients.ingredient" a lot. To me, an 'ingredient' is the food/liquid/whatever AS IT IS USED IN THE RECIPE, so the join table should be called 'ingredients'. Each ingredient has a quantity and links to a 'product' or an 'item' or something similar.

I would rename it thus:

Recipe
  has_many :ingredients
  has_many :items, :through => :ingredients

Ingredient
  #fields - recipe_id, item_id, quantity(string)
  belongs_to :recipe
  belongs_to :item

Item
  has_many :ingredients
  has_many :recipes, :through => :ingredients

Now on your view page you can say

<h2><%= recipe.name %></h2>
<dl>
  <% @recipe.ingredients.each do |ingredient| %>
    <dt><%= ingredient.item.name %></dt>
    <dd><%= ingredient.quantity %></dd>
  <% end %>
</dl>